Below is a logic-based, section-by-section note with nothing omitted, built so each fact connects causally to the next.

ADRENAL GLAND — LOGIC-BASED NOTES

1️⃣ Anatomy of the Adrenal Gland (Structure → Blood flow → Drainage)

📍 Location & Size

• Adrenal glands rest on the upper poles of the kidneys
• Each gland weighs 4–5 g
• Small size but very high vascularity → essential for rapid hormone release

🩸 Arterial Blood Supply (Why 3 sources?)

The adrenal gland needs continuous, high-volume blood flow → therefore multiple arterial inputs:

1. Inferior phrenic artery
2. Renal artery
3. Abdominal aorta

➡️ This redundancy ensures uninterrupted steroid delivery, even with fluctuations in renal flow.

🩺 Venous Drainage (Asymmetry is important)

• Right adrenal vein → directly into IVC
• Left adrenal vein → left renal vein

🔑 Clinical logic:

• Right adrenal vein is short and fragile → higher risk during surgery
• Left side is longer → drains via renal vein

🌱 Lymphatic Drainage

• Lymph drains medially
• Ends in para-aortic (aortic) lymph nodes

➡️ Important in malignancy spread.

🧱 Internal Structure (Two functionally different organs)

Each adrenal gland has two embryologically and functionally distinct parts:

1. Adrenal Cortex → steroid hormones
2. Adrenal Medulla → catecholamines (not covered here)

2️⃣ Adrenal Cortex — Zonal Organization (Structure determines function)

From outside → inside:

1. Zona glomerulosa
2. Zona fasciculata
3. Zona reticularis

🧠 Logic rule:

Each zone = different enzymes → different hormone

3️⃣ Physiology of the Adrenal Cortex — Steroid Synthesis

🔬 Core Principle

• ALL adrenocortical hormones are steroids
• ALL are derived from cholesterol

➡️ Therefore:

• Lipid-soluble
• Not stored in vesicles
• Synthesized on demand

🧪 Three Classes of Steroid Hormones

4️⃣ Transport & Metabolism of Adrenocortical Hormones

🚚 Transport in Blood (Binding determines availability)

Cortisol

• >90% bound to:
• Cortisol-binding globulin (CBG / transcortin)
• Only free cortisol is biologically active

Aldosterone

• Only ~50% protein bound
• More free hormone → faster action

🧹 Metabolism & Excretion (Why liver matters)

• All adrenocortical steroids are:
• Degraded in liver
• Conjugated mainly to glucuronides
• Smaller amounts → sulfates

Excretion

• ~75% in urine
• ~25% via bile → stool

5️⃣ Control of Hormone Synthesis — Glucocorticoids & Androgens

🎯 Big Picture

• Controlled by the hypothalamo–pituitary–adrenal (HPA) axis
• Same control system regulates:
• Cortisol
• Adrenal androgen precursors

📊 Cortisol Basics

• 95% of glucocorticoid activity = cortisol
• Remaining = corticosterone (less potent)
• Mean plasma cortisol ≈ 12 µg/dL
• Daily secretion ≈ 15–20 mg/day

6️⃣ Hypothalamic Control — CRH Release

🧠 Origin

• Paraventricular nucleus of hypothalamus

🔗 Hormone

• Corticotrophin-releasing hormone (CRH)
• 41-amino-acid peptide

🚦 Pathway

1. Released into median eminence
2. Travels via hypophysial portal circulation
3. Reaches anterior pituitary corticotrophs

➡️ Stimulates:

• ACTH synthesis
• ACTH release

7️⃣ Pituitary Control — ACTH & POMC

🧬 ACTH Origin

• ACTH derived from pro-opiomelanocortin (POMC)

🔪 POMC Cleavage

• POMC → cleaved by specific peptidases
• Can produce:
• ACTH
• MSH
• Opioid peptides

🔑 Logic:

• In corticotroph cells → ACTH predominates
• In brain → other peptides dominate

8️⃣ ACTH Actions on the Adrenal Cortex (Immediate + Long-term)

⚡ Immediate Steroidogenic Actions

ACTH acts via a G-protein-coupled receptor and causes:

1. ↑ Cholesterol esterase
2. ↑ Transport of cholesterol into mitochondria
3. ↑ Binding of cholesterol to CYP11A1

➡️ CYP11A1 = rate-limiting enzyme of steroid synthesis

🧬 Long-Term Effects

Chronic ACTH stimulation leads to:

• ↑ Steroidogenic enzyme expression
• Hypervascularisation
• Cellular hypertrophy
• Cellular hyperplasia

➡️ Explains adrenal enlargement in ACTH excess.

9️⃣ Role of Arginine Vasopressin (AVP)

🔗 AVP = ACTH Potentiator

• AVP enhances CRH action on corticotrophs

🧠 Two Sources of AVP

1. Parvocellular neurons
• Release AVP into portal circulation
• Works with CRH
2. Magnocellular neurons
• Release AVP into systemic circulation
• Controlled by:
• Plasma osmolality
• Blood volume

🔄 Negative Feedback Control (Stability mechanism)

How feedback works:

• Circulating glucocorticoids are detected by:
• Hypothalamus
• Anterior pituitary

➡️ Results in:

• ↓ CRH
• ↓ AVP (parvocellular)
• ↓ ACTH

➡️ Maintains stable cortisol levels

⏰ Circadian Rhythm of Cortisol

• Peak: Early morning
• Nadir: Evening

🔑 Logic:

• ACTH follows same rhythm
• Adrenal androgens parallel cortisol secretion
• Negative feedback fine-tunes the rhythm

🌍 Extra-Hypothalamic CRH (Important extensions)

Placenta

• Produces:
• CRH
• CRH-binding protein (CRH-BP)
• Role in initiation of parturition

Immune System

• CRH receptors present on immune cells
• CRH can be:
• Pro-inflammatory
• Anti-inflammatory

🔟 Control of Mineralocorticoids — Aldosterone

🎯 Key Principle

Aldosterone is NOT ACTH-dependent

Primary regulators:

1. Renin–angiotensin system
2. Plasma K⁺ concentration

1️⃣1️⃣ Renin–Angiotensin–Aldosterone System (RAAS)

Step-by-step logic:

1. Renin released from:
• Granular (juxtaglomerular) cells
• Afferent arteriole of kidney
2. Renin converts:
• Angiotensinogen (liver) → Angiotensin I
3. In lungs:
• ACE converts Ang I → Angiotensin II
4. Angiotensin II causes:
• Potent vasoconstriction
• Stimulation of aldosterone release from adrenal cortex

➡️ Final effect:

• Na⁺ retention
• K⁺ excretion
• Volume expansion

🔚 Final Big-Picture Integration

• Cortex = steroid factory
• ACTH controls cortisol & androgens
• RAAS + K⁺ control aldosterone
• Feedback loops + circadian rhythm maintain precision

Actions of Adrenocortical Steroids — Logic-Based Notes

I. Glucocorticoids (Cortisol)

Big Picture Logic

Cortisol’s job is to maintain energy availability during stress and limit excessive inflammation, even if that comes at a cost to tissues and immunity.

1️⃣ Effect on Glucose Metabolism

Core action:

→ Stimulates gluconeogenesis (mainly in the liver)

Logical chain:

• Cortisol ↑ hepatic gluconeogenic enzymes
• Amino acids + glycerol are converted to glucose
• → Serum glucose concentration increases

Why this matters:

• Ensures glucose supply to brain and vital organs
• Explains steroid-induced hyperglycemia and diabetes risk

2️⃣ Effect on Protein Metabolism (Catabolic Effect)

Core action:

→ Protein breakdown exceeds synthesis

Logical chain:

• Cortisol ↑ proteolysis in muscle and connective tissue
• Amino acids released → used for gluconeogenesis
• → Decrease in body protein stores

Clinical logic:

• Muscle wasting
• Thin skin
• Poor wound healing

3️⃣ Anti-Inflammatory Effects (Clinically Significant)

Core action:

→ Suppresses inflammatory response

Logical chain:

• ↓ cytokine production
• ↓ prostaglandins and leukotrienes
• ↓ capillary permeability
• ↓ leukocyte migration to tissues

Why this is important:

• Basis for therapeutic use of corticosteroids
• Powerful symptom control in inflammatory and autoimmune diseases

4️⃣ Effects on Immunity (Adverse)

Core action:

→ Immunosuppression

Logical chain:

• ↓ circulating eosinophils and lymphocytes
• Causes atrophy of lymphoid tissue
• ↓ cell-mediated immunity

Clinical implication:

• ↑ susceptibility to infections
• Masking of infection signs

II. Adrenal Androgens

Big Picture Logic

Adrenal androgens are weak by themselves, but become important after peripheral (extra-adrenal) conversion.

1️⃣ Hormones Secreted

The adrenal cortex continuously secretes:

• DHEA
• DHEAS
• Androstenedione
• 11-hydroxyandrostenedione
• Small quantities of:
• Progesterone
• Estrogen

2️⃣ Strength of Action

Key fact:

→ All have weak intrinsic androgenic effects

3️⃣ Role in Males (Boys)

Logical role:

• Contribute to early development of male sex organs
• Act before full testicular testosterone dominance

4️⃣ Role in Females (Girls)

Logical role:

• Important during puberty and menarche
• Contribute to:
• Pubic and axillary hair
• Libido

5️⃣ Extra-Adrenal Conversion (Key Concept)

Most androgenic effects occur because:

• Adrenal androgens → converted to testosterone in peripheral tissues

Exam logic:

• Explains virilization in adrenal disorders
• Explains androgen effects despite “weak” hormones

III. Mineralocorticoids (Aldosterone)

Big Picture Logic

Aldosterone’s role is volume regulation, not sodium concentration regulation.

1️⃣ Dominance of Aldosterone

• Aldosterone = 90% of total mineralocorticoid activity

2️⃣ Renal Tubular Actions

Site of action:

• Distal tubules
• Collecting ducts

Core actions:

• ↑ Na⁺ reabsorption
• ↑ K⁺ excretion

3️⃣ Water Balance & Volume

Logical chain:

• Na⁺ reabsorbed → H₂O follows passively
• → ↑ Extracellular fluid (ECF) volume
• Plasma Na⁺ concentration changes little

4️⃣ Blood Pressure Effects

Persistent elevation of ECF volume →

• Hypertension

5️⃣ Aldosterone Deficiency

Without aldosterone:

• Excessive Na⁺ loss
• H₂O lost with Na⁺
• → Fluid depletion
• → Hypotension and shock risk

IV. Steroid Transport and Metabolism

Big Picture Logic

Only free hormone is active, but most steroids circulate bound for stability and transport.

1️⃣ Cortisol Transport

• Binds mainly to cortisol-binding globulin (CBG / transcortin)
• >90% of cortisol is protein-bound
• Only free cortisol is biologically active

2️⃣ Aldosterone Transport

• Only ~50% bound to protein
• Higher free fraction → rapid action but short half-life

3️⃣ Metabolism

All adrenocortical steroids:

• Degraded in the liver
• Conjugated mainly to:
• Glucuronides
• Smaller amounts of sulphates

4️⃣ Excretion

Final fate:

• ~75% excreted in urine
• Remaining portion:
• Excreted in stool via bile

Final Integrated Memory Logic

• Cortisol → energy supply + inflammation control (at cost of immunity & tissue)
• Adrenal androgens → weak alone, powerful after peripheral conversion
• Aldosterone → volume control → blood pressure regulation
• Transport & metabolism → protein binding, liver conjugation, renal & biliary excretion

Physiology of the Adrenal Medulla — Logic-Based Notes (Section by Section, Zero Omission)

1) Structure + Blood Supply (Why the medulla is “set up” the way it is)

• Size/portion
• Adrenal medulla = < 20% of the adrenal gland.
• Histology
• Cells are polygonal.
• Arranged in cords.
• Blood supply routes (key logic = cortisol-rich blood influences medullary output)
• Medulla receives blood:
1. Directly from medullary arterioles, OR
2. From cortical venules (this blood is rich in cortisol) and drains centripetally to the medullary venules.
• Meaning: medulla is bathed in cortisol-rich cortical drainage, especially near the corticomedullary junction.

2) What the medulla makes + how secretion is triggered (Neural control → hormone release)

• Main products
• Epinephrine (major)
• Norepinephrine (smaller amounts)
• Where made
• Synthesised by and secreted from chromaffin cells in the medulla.
• Trigger
• Preganglionic (cholinergic) sympathetic nerves stimulate chromaffin cells.
• These preganglionic fibres originate in thoracolumbar lateral grey matter of the spinal cord.
• Why “chromaffin”
• Named due to affinity for chromium salts → gives characteristic staining.
• What chromaffin cells really are (logic = neuron-like behavior)
• They are modified postganglionic nerve cells.
• They are classic neurosecretory cells = neurons releasing hormones into the general circulation.

3) Catecholamine synthesis (Tyrosine pathway, single-tyrosine logic)

• Starting material
• Catecholamines are synthesised from tyrosine.
• Like melatonin and thyroid hormones, they come from tyrosine—but difference:
• Catecholamines are made from single tyrosine molecules (thyroid hormones are not, in contrast).
• Where tyrosine comes from
• Tyrosine is either:
• Synthesised from phenylalanine, OR
• Imported from the circulation.
• Rate-limiting step (the “bottleneck”)
• Tyrosine hydroxylase converts:
• Tyrosine → 3,4-dihydroxyphenylalanine (DOPA).
• This is the rate-limiting step in catecholamine synthesis.
• Stepwise pathway (enzyme → product)
1. Tyrosine —(tyrosine hydroxylase)→ DOPA
2. DOPA —(aromatic-L-amino-acid decarboxylase)→ dopamine
3. Dopamine —(dopamine β-hydroxylase, hydroxylation)→ norepinephrine
4. Norepinephrine —(phenylethanolamine N-methyltransferase, PNMT)→ epinephrine
• This final conversion happens in most cells, especially those at the corticomedullary junction.
• In some medullary cells, synthesis stops at norepinephrine.

4) Control of output + cellular secretion mechanism (Hypothalamus → ACh → Ca²⁺ → exocytosis)

• Master control center
• Output is controlled by nerve cells in the posterior hypothalamus.
• How hypothalamus drives medulla
• Ultimately stimulates acetylcholine (ACh) release from preganglionic nerve terminals.
• What ACh does to chromaffin cells
• Causes depolarisation of chromaffin cells.
• Leads to exocytosis of catecholamine-containing granules.
• Immediate intracellular event that enables exocytosis
• Exocytosis follows a transient rise in intracellular Ca²⁺ concentration.
• Circulating half-life (why effects are rapid + brief unless continuously stimulated)
• Catecholamines have a very short half-life in blood:
• ~ 1–2 minutes.

5) Actions of catecholamines (Receptor logic: GPCR → α vs β, “fight or flight”)

• Receptor type
• Act via typical G-protein-linked membrane receptors (GPCRs).
• Receptor classes
• Alpha-adrenergic receptors
• Beta-adrenergic receptors
• Classification based on physiological + pharmacological effects when hormone binds.
• Overall physiological role (“fight or flight” package)
• Prepare the body for acute stress with:
• ↑ heart rate and ↑ stroke volume
• ↑ blood pressure
• bronchodilatation
• mobilisation of glucose
• stimulation of lipolysis
• These “fight/flight” actions are stated as being mediated by β-adrenergic receptors in this text.
• Blood flow redistribution (logic = shunt away from gut → toward skeletal muscle)
• Blood flow to splanchnic bed decreases via arteriolar vasoconstriction.
• This is mediated by α-adrenergic receptors.
• Purpose: divert blood flow to skeletal muscles.

6) Metabolism + clearance (Uptake 1 vs Uptake 2 → MAO/COMT → urinary metabolites)

• What happens to catecholamines from sympathetic nerves
• Most released from sympathetic nerves are taken back into presynaptic terminal:
• Uptake 1.
• What happens to circulating catecholamines (from adrenal medulla)
• Taken up by non-neuronal tissues:
• Uptake 2.
• Key metabolic enzymes
• Rapid conversion to:
• Deaminated products by monoamine oxidase (MAO), OR
• O-methylated products by catechol O-methyltransferase (COMT).
• COMT does an extra job
• COMT also catalyses m-O-methylation of the products of MAO action, listed here as:
• metanephrine
• normetanephrine
• epinephrine
• vanillylmandelic acid (VMA)
• Final processing + excretion
• These metabolites may be conjugated with:
• glucuronide or sulphate
• Then excreted in urine.

7) Table 17.1 — Effects of catecholamines (System-by-system with mediator)

A) Cardiovascular

• ↑ Heart rate + force → β1 receptors
• ↑ Venous return → α receptors
• ↑ Peripheral resistance → α receptors
• Especially in subcutaneous, mucosal, splanchnic, and renal vascular beds

B) Autonomic nervous system

• Smooth muscle relaxation → β2 receptors
• Smooth muscle contraction → α receptors
• Modulation of fluid + electrolyte transport in:
• gut, kidney, gallbladder → α receptors

C) Fuel metabolism

• Glycogenolysis + lipolysis → β receptors
• ↑ Diet-induced + nonshivering thermogenesis → β receptors

D) Fluid and electrolyte balance

• ↓ Na⁺ excretion + ↓ glomerular filtration → direct effects on the kidney
• ↑ Aldosterone production → ↑ Na⁺ retention in distal tubule
• via β-receptor–mediated effects on renin secretion
• ↑ Serum K⁺ → α-receptor–mediated effects on the liver
• ↓ Serum K⁺ → β2-receptor–mediated effects on muscle

E) Endocrine

• Modulation of renin–angiotensin–aldosterone system → β1 receptors
• ↑ Secretion of glucagon and insulin → β2 receptors
• Inhibition of carbachol-stimulated synthesis of catecholamines → α2 receptors

DISEASES OF THE ADRENAL GLAND

SECTION 1 — CUSHING SYNDROME

1️⃣ Core Concept (Big Picture Logic)

• Cushing syndrome = excess glucocorticoids (cortisol)

→ regardless of source.

• Cushing disease is a subset:
• Excess cortisol specifically due to ACTH-secreting pituitary tumour.

👉 Logic:

• All Cushing disease = Cushing syndrome
• Not all Cushing syndrome = Cushing disease

2️⃣ ACTH-Dependent vs ACTH-Independent Logic

A. Pituitary ACTH excess (Cushing disease)

• Pituitary tumour secretes ACTH
• → Bilateral adrenal hyperplasia
• → Excess cortisol

B. Ectopic ACTH secretion

• ACTH produced outside pituitary
• Example: lung tumour
• Clinical features may be atypical

Why atypical?

• Very high ACTH → very high cortisol
• Cortisol acts on mineralocorticoid receptors
• → Hypokalaemia
• → Metabolic alkalosis

👉 Key exam logic:

• Hypokalaemia + alkalosis = think ectopic ACTH

3️⃣ Clinical Features (Logical Grouping)

(You referenced Tables 17.2 & 17.3 — we keep logic intact)

A. Features due to cortisol excess

• Glucose intolerance / diabetes
• Muscle wasting
• Thin skin, easy bruising
• Central obesity
• Hypertension
• Osteoporosis
• Immunosuppression

B. Features due to pituitary tumour (if present)

Loss of other pituitary hormones may coexist:

• ↓ TSH → hypothyroidism
• ↓ LH/FSH → hypogonadism
• ↓ GH → growth hormone deficiency

👉 Logic:

• Pituitary adenoma compresses normal pituitary tissue
• → panhypopituitarism features

4️⃣ Diagnosis — Screening Tests (WHY these tests work)

A. 24-hour urinary free cortisol

• Measures total cortisol production
• Bypasses circadian rhythm issues

B. Midnight salivary cortisol

• Normal physiology: cortisol should be lowest at midnight
• Loss of diurnal rhythm = Cushing syndrome

C. Low-dose dexamethasone suppression test

• Dexamethasone should suppress ACTH
• Failure to suppress = autonomous cortisol production

5️⃣ Differentiation Logic (CRH + Dexamethasone)

Used to distinguish:

• Pseudo-Cushing (obesity, alcoholism, depression)
• Pituitary ACTH excess
• Primary adrenal disease
• Ectopic ACTH

👉 Key logic:

• Pituitary tumours may still respond to CRH
• Ectopic ACTH tumours usually do not

6️⃣ Imaging — Why Each Modality Is Used

A. Adrenal lesions

CT (unenhanced / delayed contrast)

• Benign lesions = fat-rich
• Fat → low attenuation

MRI

• Better tissue characterisation
• Gadolinium enhancement
• Chemical shift imaging
• Superior benign vs malignant differentiation

Ultrasonography (especially in children)

• First-line in paediatrics
• Differentiates:
• Cystic vs solid masses
• Assesses:
• Vascular involvement
• Liver metastases

Radioisotope scanning

• Rarely used now

B. Pituitary lesions

• MRI = imaging modality of choice
• Visual field testing:
• Large tumours → bitemporal hemianopia

👉 Logic:

• Compression of optic chiasm from below

7️⃣ Treatment — Definitive vs Supportive

A. Definitive Treatment = Surgery

• Pituitary disease → Transsphenoidal surgery
• Adrenal disease → Adrenalectomy
• Laparoscopic or open

B. Medical / Supportive Management

Correct complications

• Hypokalaemia:
• K⁺-sparing diuretics
• Potassium supplements

C. Drugs Used (Grouped by Mechanism)

1. Somatostatin analogues

• Example: Pasireotide
• ↓ ACTH secretion

2. Adrenal steroid inhibitors

• Metyrapone
• Ketoconazole
• Aminoglutethimide
• Mifepristone

👉 Logic:

• Either block cortisol synthesis
• Or block cortisol receptor action

SECTION 2 — PRIMARY ALDOSTERONISM (CONN SYNDROME)

1️⃣ Core Concept (Physiology Logic)

• Excess mineralocorticoid (aldosterone)
• Kidney effects:
• ↑ Na⁺ reabsorption
• ↑ H₂O retention
• ↑ K⁺ loss

Consequences:

• Hypertension
• Hypokalaemia
• Suppressed renin

👉 Pathophysiology chain:

Aldosterone ↑ → Volume ↑ → Renin ↓

2️⃣ Epidemiology

• Accounts for up to 2% of all hypertension
• Important because it is potentially curable

3️⃣ Causes (With Percentages)

A. Adrenal adenoma (≈ 80%)

• Solitary adenoma: 65–70%
• Multiple adenomas: 13%
• Microadenomatosis: 6%

B. Adrenal hyperplasia: 20%

C. Adrenal carcinoma: < 1%

4️⃣ Clinical Presentation — When to Suspect It

Red-flag scenarios:

• Spontaneous hypokalaemia + hypertension
• Severe hypokalaemia with low–moderate diuretic doses
• Treatment-resistant hypertension

Symptoms of severe hypokalaemia

• Fatigue
• Muscle weakness
• Muscle cramps
• Headaches
• Palpitations

Renal effects of hypokalaemia

• Nephrogenic diabetes insipidus
• → Polydipsia
• → Polyuria

Long-standing hypertension complications

• Cardiac
• Retinal
• Renal
• Neurological

5️⃣ Diagnosis — Biochemical Logic

Classic biochemical triad:

• Hypokalaemia
• Metabolic alkalosis
• Hyperaldosteronism

6️⃣ Screening Test — Aldosterone/Renin Ratio (ARR)

Why this works:

• Aldosterone high
• Renin suppressed
• Ratio stays consistently elevated

Measurement conditions:

• Measure PRA + PAC simultaneously
• Stop interfering antihypertensive drugs

Diagnostic cut-offs:

If aldosterone in ng/dL and PRA in ng/mL/h:

• ARR > 20–25
• Sensitivity: 95%
• Specificity: 75%

If aldosterone in pmol/L:

• ARR > 900 → consistent with primary aldosteronism

FINAL LOGIC LOCK (EXAM MEMORY)

• Cushing syndrome = cortisol excess
• Cushing disease = pituitary ACTH tumour
• Ectopic ACTH → hypokalaemia + alkalosis
• Primary aldosteronism:
• HTN + hypokalaemia
• Renin suppressed
• ARR elevated
• Often surgically curable

1) Genetic–Familial Primary Aldosteronism (Familial Hyperaldosteronism) — “What genetic types exist?”

Core logic

Primary aldosteronism can run in families due to specific genetic mechanisms. The text describes 3 distinct familial varieties:

Varieties (3 types)

• Type 1: Glucocorticoid-remediable aldosteronism (GRA)
• Key logic: aldosterone excess is glucocorticoid-remediable / glucocorticoid-sensitive
• Type 2: Familial primary aldosteronism (non-glucocorticoid sensitive)
• Key logic: not glucocorticoid sensitive
• Type 3: Familial primary aldosteronism due to potassium channel mutations
• Key logic: aldosterone excess driven by K⁺ channel mutations

2) Primary Aldosteronism — Treatment (and why you must separate tumour vs hyperplasia)

Core logic

Treatment depends on whether aldosterone excess is from:

• A solitary aldosterone-producing tumour (APA) vs
• Bilateral adrenal hyperplasia

Because:

• Surgery helps tumour cases,
• Surgery should be avoided in bilateral hyperplasia.

Surgical treatment (solitary tumour)

• In 75–90% of people with a solitary aldosterone-producing tumour, surgical adrenalectomy:
• Corrects hypertension
• Corrects hypokalaemia

When NOT to do surgery

• Avoid surgery in bilateral hyperplasia

How to distinguish tumour vs bilateral hyperplasia (must-do step)

• CT or MRI are the best modalities to:
• Localise a tumour, or
• Establish bilateral adrenal hyperplasia
• (Text explicitly parallels this importance with Cushing syndrome workup: localisation matters.)

If hyperplasia is present (medical therapy)

Goal:

• Correct hypokalaemia
• Treat hypertension

Drugs (as per text)

• Mineralocorticoid antagonists e.g. spironolactone
• Adverse effects (estrogen-like):
• Impotence
• Gynaecomastia
• Eplerenone
• Selective anti-aldosterone agent
• Specific aldosterone-receptor antagonist
• Does NOT have the additional antiandrogen effects associated with spironolactone

Specific treatment for GRA

• Small doses of glucocorticosteroids:
• Hydrocortisone or prednisone
• At optimal doses:
• Normalise aldosterone
• Normalise blood pressure

3) Phaeochromocytoma — “What is it, where is it, what does it secrete, how dangerous?”

Definition + sites

• A phaeochromocytoma = rare catecholamine-secreting tumour of the sympathetic nervous system
• Site distribution:
• 90% arise from adrenal sites
• 10% occur elsewhere in the sympathetic chain
• Tumours outside the adrenal gland are called:
• Extra-adrenal phaeochromocytomas or paragangliomas

What catecholamines are released (and what pattern suggests size/site)

• Most tumours release:
• Both epinephrine and norepinephrine
• But:
• Large and extra-adrenal tumours produce almost entirely norepinephrine

Why it’s dangerous

• Excess catecholamines may precipitate:
• Life-threatening hypertension
• Cardiac arrhythmias

Malignancy + curability

• Malignant in 10% of cases
• May be cured completely by surgical removal

Genetics / syndromes (classical vs updated)

• Classically associated with 3 syndromes:
• VHL (von Hippel-Lindau)
• MEN 2
• NF1
• Now:
• 10 genes have been identified as mutation sites leading to phaeochromocytoma
• Clinical implication stated:
• Family history is important because germline mutations may underlie familial forms

4) Phaeochromocytoma — Diagnosis (choose test based on suspicion; sensitivity vs specificity)

Core logic

• Pick a test depending on how strongly you suspect it.
• Understand:
• High sensitivity = good to rule out
• High specificity = good to rule in

Biochemical tests (with exact performance figures from text)

1. Plasma metanephrines

• Highest sensitivity: 96%
• Lower specificity: 85%

1. 24-hour urinary catecholamines + metanephrines

• Sensitivity: 87.5%
• Specificity: 99.7%

Localisation imaging

• Usually localised with:
• CT or MRI

If biochemically confirmed but CT/MRI negative

• Use iodine-123 (123I)–labelled MIBG scan
• Reserved for cases where:
• Phaeochromocytoma is confirmed biochemically
• But CT/MRI does not show a tumour

Alternative nuclear imaging mentioned

• 111In pentetreotide (somatostatin-receptor analogue)
• Less sensitive than MIBG
• But can visualise tumours that do not concentrate MIBG

PET imaging

• 18F-FDG PET
• Detects occult tumours based on abnormal metabolism (FDG selectively concentrated in many neoplasms)
• Has been demonstrated to detect occult phaeochromocytomas

5) Phaeochromocytoma — Treatment (why you MUST block alpha first)

Core logic

• Only curative option = remove tumour.
• But catecholamine surges during anaesthesia/surgery can kill → you pre-treat to stabilise.

Definitive cure

• Complete surgical removal of tumour
• Only form of curative therapy

Why careful pre-op management is required

Pre-op management aims to:

• Control blood pressure
• Correct fluid volume
• Prevent intraoperative hypertensive crises
• Reduce risk of acute catecholamine release triggered by:
• Anaesthetic drugs
• Surgical handling

Standard pre-operative blockade sequence (as stated)

• Initially α-adrenergic blockade
• Followed by:
• Combination of α-adrenergic and β-adrenergic blockade

6) Hypoadrenalism — “Primary vs secondary, and autoimmune syndromes”

Core logic

Hypoadrenalism can be:

• Primary adrenal insufficiency (Addison’s disease), OR
• Secondary to pituitary damage → reduced adrenal cortical hormone production

(The text notes causes are summarised in Table 17.5, but the key explanatory content given is autoimmune.)

Autoimmune Addison’s disease: isolated vs multi-organ

• Autoimmune adrenal destruction may be:
• Isolated, or
• Part of multi-organ involvement

Two autoimmune polyendocrinopathy types

APS Type 1 (APECED)

• Also called:
• APECED = autoimmune polyendocrinopathy, candidiasis, ectodermal dystrophy
• Occurs with:
• Autoimmune hypoparathyroidism
• Chronic mucocutaneous candidiasis
• Other organ-specific autoimmune disorders
• Inheritance and nature:
• Monogenic autoimmune disorder
• Autosomal recessive inheritance

APS Type 2 (Schmidt syndrome)

• Association:
• Autoimmune Addison’s disease + autoimmune thyroid disease and/or type 1 diabetes
• Epidemiology:
• Predilection for women in middle age
• Average onset 35–40 years
• Genetics:
• Genetic basis not clearly understood for:
• Isolated autoimmune Addison’s
• APS type 2
• Other autoimmune disorders that can be associated:
• Primary gonadal failure
• Pernicious anaemia
• Vitiligo
• Alopecia
• Mechanism statement:
• Antibodies to the adrenal cortex mediate autoimmune destruction

Clinical features clue in text

• High ACTH → pigmentation:
• Buccal pigmentation
• Pigmentation of scars
• Pigmentation of palmar creases
• (Clinical features otherwise referenced as Table 17.6.)

7) Hypoadrenalism — Diagnosis (routine labs → confirm with tetracosactrin test → interpret ACTH)

Screening clue from routine biochemistry

Suspicion can come from:

• Hyponatraemia
• Hyperkalaemia
• Hypercalcaemia

Biochemical confirmation: tetracosactrin test (ACTH stimulation)

• Tetracosactrin = peptide identical to the first 24 amino-terminal amino acids of ACTH Process:

1. Measure baseline ACTH and cortisol (peripheral venous blood)
2. Give single injection of 250 micrograms tetracosactrin
3. Measure cortisol again at 30 minutes (text also later refers to 30 or 60 minutes in criteria)

Diagnostic criteria (two criteria required)

1. Cortisol increases from baseline by 7 micrograms/dl or more
2. Cortisol must rise to 20 micrograms or more by 30 or 60 minutes → This establishes normal adrenal glucocorticoid function

Interpretation nuance (important exam trap from text)

• The absolute 30- or 60-minute cortisol value is more significant than the incremental rise
• Especially in patients under great stress who may already be at maximal adrenal output

Differentiate primary vs secondary using baseline ACTH

If cortisol response is impaired:

• High baseline ACTH → primary adrenal failure
• Low baseline ACTH → secondary adrenal failure

Physiology logic stated:

• Primary disease: stimulation will not result in cortisol release
• Secondary insufficiency: adrenal glands are atrophic but can still make some cortisol with ACTH
• Serum cortisol rises to more than 1000 nmol/L when exposed to ACTH (as per text)

8) Hypoadrenalism — Imaging (what CT/MRI show and what MRI can/can’t do)

Why imaging helps

• Imaging can help elucidate the cause of hypoadrenalism

CT and MRI patterns described

• Autoimmune destruction:
• Reduced adrenal gland size on CT/MRI
• Infection (e.g., TB):
• Enlarged adrenal gland on CT/MRI

MRI vs CT (specific comparison stated)

• MRI is superior to CT in differentiating adrenal masses
• But:
• MRI cannot distinguish:
• A tumour vs
• An inflammatory process

9) Hypoadrenalism — Treatment (acute crisis vs long-term replacement + patient education)

A) Acute adrenal crisis (emergency management)

Immediate steps:

• Establish IV access urgently
• Start isotonic sodium chloride infusion to:
• Restore volume deficit
• Correct hypotension
• Some patients may require glucose supplementation
• Identify and correct the precipitating cause where possible

Steroid therapy (exact doses given)

• Immediate IV hydrocortisone 100 mg
• Then 100–200 mg hydrocortisone over 24 hours
• Under close monitoring

B) Long-term replacement (stable adrenal insufficiency)

• Usually 2 or 3 daily doses of hydrocortisone
• “Stress dosing” logic:
• Extra dose before strenuous exercise
• Doses are usually doubled for intercurrent illness

Mineralocorticoid replacement (standard)

• Fludrocortisone acetate 100–150 micrograms/day
• Dose titrated individually using:
• Clinical examination (mainly body weight and arterial BP)
• Plasma renin activity levels

Key rule: when mineralocorticoid isn’t needed

• If patient is receiving 100 mg or more hydrocortisone in 24 hours:
• No mineralocorticoid replacement is necessary
• Because hydrocortisone’s mineralocorticoid activity at that dose is sufficient

Women and androgens (replacement consideration)

• In women, adrenal cortex is primary androgen source:
• DHEA and DHEAS
• Physiological role not fully elucidated, but:
• Replacement is being increasingly considered in adrenal insufficiency treatment

C) Patient education (explicit list from text)

• Wear an emergency medical alert bracelet
• Double or triple steroid doses in stressful situations:
• e.g., common cold, tooth extraction
• Contact physician / go to ED in case of illness
• Learn to give intramuscular injections
• Given a prescription for parenteral hydrocortisone for:
• When oral intake not possible, or
• Marked vomiting/diarrhoea occurs
• No adjustment needed for mineralocorticoid dose in stressful situations

10) Congenital Adrenal Hyperplasia (CAH) — Definition, commonest cause, and why phenotype varies

Definition (group concept)

• CAH = group of autosomal recessive disorders
• Each involves deficiency of an enzyme needed for synthesis of:
• Cortisol
• Aldosterone
• Or both

Most common form (with proportion and gene)

• 21-hydroxylase deficiency
• Due to mutations/deletions of CYP21A
• Accounts for >90% of CAH cases

Why presentation varies

• Clinical phenotype depends on:
• Nature and severity of enzyme deficiency

Neonatal sex ambiguity (key general statement)

• In neonates with CAH, sex may be unclear initially due to genital ambiguity

Severe salt-wasting presentation (timing + features)

• If defect severe → salt wasting:
• Presents at age 1–4 weeks with:
• Failure to thrive
• Recurrent vomiting
• Dehydration
• Hypotension
• Hyponatraemia
• Hyperkalaemia
• Shock
• Named by text as:
• Classic salt-wasting adrenal hyperplasia

11) CAH — Clinical presentation (sectioned exactly as in text: females vs males vs specific enzyme defects)

Females

• Severe CAH due to:
• 21-hydroxylase deficiency
• 11-β-hydroxylase deficiency
• 3-β-hydroxysteroid dehydrogenase deficiency → Ambiguous genitalia at birth
• Called: classic virilising adrenal hyperplasia
• Mild 21-hydroxylase deficiency:
• Identified later in childhood because of:
• Precocious pubic hair
• Clitoromegaly
• Or both
• Often with:
• Accelerated growth
• Advanced skeletal maturation
• Called: simple virilising adrenal hyperplasia
• Still milder deficiencies of:
• 21-hydroxylase, or
• 3-β-hydroxysteroid dehydrogenase → Present in adolescence/adulthood with:
• Oligomenorrhoea
• Hirsutism
• And/or infertility
• Called: nonclassical adrenal hyperplasia
• 17-hydroxylase deficiency:
• Phenotypically female at birth
• In adolescence:
• Do not develop breasts
• Do not menstruate
• May present with hypertension

Males

• 21-hydroxylase deficiency:
• Normal genitalia (important: may be missed until salt-wasting crisis unless screened)

12) CAH — Diagnosis (prove low final hormones + high precursors; then specify by enzyme type)

Core logic

Diagnosis relies on showing:

• Inadequate production of cortisol, aldosterone, or both
• With accumulation of precursor hormones in excess

21-hydroxylase deficiency (key diagnostic markers)

• High serum 17-hydroxyprogesterone
• Usually >1000 ng/dl
• High urinary pregnanetriol
• Metabolite of 17-hydroxyprogesterone
• Must be in the presence of clinical features suggestive of disease

Nonclassical cases

• Use tetracosactrin-stimulation test to diagnose CAH (as stated)

11-β-hydroxylase deficiency (markers)

• Excess serum:
• 11-deoxycortisol
• Deoxycorticosterone
• OR elevated urinary ratio:
• Tetrahydrocompound S (metabolite of 11-deoxycortisol)
• to tetrahydrocompound F (metabolite of cortisol)
• (Ratio over 24-hour urine collection)

Salt-wasting forms (biochemistry pattern)

• Low aldosterone
• Hyponatraemia
• Hyperkalaemia
• Elevated plasma renin activity (PRA)
• Indicates hypovolaemia

13) CAH — Imaging and other investigations (what each test answers)

Pelvic ultrasonography

• In an infant with ambiguous genitalia:
• Demonstrate a uterus
• Or associated renal anomalies

Bone age study

• Useful when child develops:
• Precocious pubic hair / clitoromegaly / accelerated linear growth
• Evaluates for advanced skeletal maturation

Karyotype

• Establish chromosomal sex

Genetic testing (stated as essential)

• Essential for:
• Genetic counselling
• Prenatal diagnosis of adrenal hyperplasia

Newborn screening (clinical importance statement)

• Screening for 21-hydroxylase deficiency may be life-saving in affected male infants
• Otherwise may be undetected until salt-wasting crisis

14) CAH — Treatment (acute salt-wasting crisis → then long-term; include Endocrine Society 2010 points)

A) Acute salt-wasting crisis management

• Treat with IV sodium chloride to restore:
• Intravascular volume
• Blood pressure
• Fluids:
• After bolus, include dextrose to prevent hypoglycaemia

Before steroids (sampling step)

• After obtaining samples to measure:
• Electrolytes
• Blood sugar
• Cortisol
• Aldosterone
• 17-hydroxyprogesterone → Treat with glucocorticoids

B) Long-term stabilised management

• After stabilisation:
• All patients treated with long-term:
• Glucocorticoid replacement
• and/or fludrocortisone replacement

C) Endocrine Society 2010 clinical practice guideline points (as listed)

• Prenatal treatment for CAH should be regarded as experimental
• Glucocorticoid therapy should be carefully titrated to avoid Cushing syndrome
• Mineralocorticoid replacement is encouraged
• In infants:
• Mineralocorticoid replacement + sodium supplementation encouraged
• Agents to delay puberty and promote growth are experimental
• Psychiatric support should be encouraged for patients with adjustment problems
• Medication should be used judiciously during:
• Pregnancy
• And in symptomatic patients with nonclassical CAH

15) CAH — Surgical care (traditional approach + when surgery may be unnecessary + guideline points)

Core logic

Surgery is about managing ambiguous genitalia, but the text emphasizes:

• Severity matters
• Medical therapy can prevent progression
• Certain surgical practices should be avoided

Surgical evaluation

• Infants with ambiguous genitalia require:
• Surgical evaluation
• Planning for corrective surgery

Traditional approach described (female ambiguous genitalia due to CAH)

• Clitoral recession early in life
• Followed by vaginoplasty after puberty

Mild virilisation caveat

• Some female infants have only mild virilisation
• May not require corrective surgery if:
• Adequate medical therapy is given to prevent further virilisation

Endocrine Society 2010 surgical guidance (as listed)

• Adrenalectomy should be avoided
• Surgical reconstruction:
• May not be necessary during newborn period in mildly virilised girls
• May be appropriate in severely virilised girls
• Should be:
• Single-stage genital repair
• Performed by *experienced surgeons

Thyroid Gland — Logic-Based Notes (Section by Section, Zero-Omission)

1) Physiology of the Thyroid Gland

1.1 What hormones does the thyroid make?

The thyroid synthesises and secretes three hormones:

1. From follicular cells

• Thyroxine (T4)
• Triiodothyronine (T3)

1. From C cells (parafollicular cells)

• Calcitonin (Calcitonin details are elsewhere; here the focus is follicular-cell hormones = “thyroid hormones”.)

2) Synthesis of Thyroid Hormones

Big logic: what the follicular cell is trying to do

The follicular cell must:

1. Bring iodide into the cell
2. Oxidise iodide and attach it to tyrosine residues on thyroglobulin (iodination)
3. Couple iodotyrosines to form T3 and T4
4. Store hormone in the colloid
5. Retrieve colloid and release T3/T4 into blood when stimulated

2.1 Iodine uptake

Core idea

Iodine is indispensable for thyroid hormone synthesis (it is a required component).

Path

• Ingested iodine → absorbed via small intestine
• Travels in plasma to thyroid
• Thyroid concentrates iodide (accumulates it above plasma levels)

Mechanism of iodide uptake (into thyroid cells)

• Iodide uptake depends on membrane ATPase
• Key transporter protein: Na⁺–iodide symporter (NIS)
• NIS is:
• Sensitive to iodine availability
• Stimulated by TSH (thyrotrophin)

Then what happens at the apical side?

• Passive transport occurs across the apical plasma membrane (from follicular cell toward follicle lumen side)

2.2 Formation of iodotyrosines and iodothyronines

Sequence

After iodide is concentrated:

1. Thyroid rapidly oxidises iodide
2. Oxidised iodine binds to tyrosyl residues in thyroglobulin
3. Then coupling of iodotyrosines forms T4 and T3

Requirements (must all be present)

• Iodide
• Peroxidase = thyroid peroxidase (TPO)
• Hydrogen peroxide (H2O2) supply
• Thyroglobulin (the iodine acceptor protein)

Where does this happen?

• At the apical plasma membrane–follicle lumen boundary (interface of cell and colloid)

Final step: coupling rules (exact)

• Two diiodotyrosines (DIT + DIT) → T4
• One diiodotyrosine + one monoiodotyrosine (DIT + MIT) → T3

2.3 Hormone storage and secretion

Storage logic

• Once thyroglobulin is iodinated and hormone is formed, you now have mature hormone-containing thyroglobulin molecules (containing T4 and T3 within the thyroglobulin structure).
• These are stored in the follicular lumen.
• This stored material forms the bulk of the thyroid follicle colloid.

Secretion logic (what TSH triggers)

When TSH stimulates:

1. Colloid is taken up into follicular cells
2. Lysosomal enzymes digest thyroglobulin
3. This releases T3 and T4 from thyroglobulin for secretion

Normal secretion estimates (euthyroid humans)

• About 100 micrograms/day of T4
• About 20 micrograms/day of T3
• Thyroid may also convert some T4 → reverse T3

3) Control of Thyroid Hormone Synthesis

3.1 TSH (thyroid-stimulating hormone / thyrotrophin)

What is TSH?

• Released from anterior pituitary
• A complex glycoprotein
• Molecular weight about 30,000 Dalton

How TSH works at the follicular cell

• Acts on G-protein–coupled transmembrane receptors on follicular cells
• This increases:
• cAMP
• phosphatidylinositol concentrations

What TSH stimulates (full list)

TSH stimulates expression/production of:

• Na⁺–iodide symporter (NIS)
• Thyroid peroxidase
• Thyroglobulin
• Generation of H2O2

TSH also:

• Increases formation of T3 relative to T4
• Alters the priority of iodination and hormonogenesis among tyrosyl residues
• Promotes rapid internalisation of thyroglobulin by thyrocytes

Negative feedback effects on TSH release (what inhibits TSH release)

TSH release is inhibited by:

• Increased T3 and T4 serum concentrations (classic negative feedback)
• Somatostatin
• Glucocorticoids
• Chronic illness

3.2 TRH (thyrotrophin-releasing hormone) and hypothalamus–pituitary feedback

TRH actions

• TRH is a hypothalamic tripeptide
• TRH:
• Stimulates TSH release from anterior pituitary thyrotrophs
• Upregulates transcription of the TSH gene

T3 receptors and feedback at pituitary/hypothalamus

• T3 receptors are present in pituitary and hypothalamus
• They inhibit:
• TSH release
• Transcription of the TRH prohormone gene

Additional note

• T3 excess also inhibits TSH release
• This feedback system helps maintain serum T3 concentrations

4) Transport and Metabolism of Thyroid Hormones

4.1 Protein binding in blood

Thyroid hormones circulate mostly bound to plasma proteins:

• ~70% bound to T4-binding globulin (TBG)
• Rest bound to:
• Transthyretin
• Albumin

Free fractions:

• Only 0.1% of T4 is free (unbound)
• Only 1% of T3 is free (unbound)

4.2 Peripheral regulation and conversion

• Peripheral tissues can regulate local T3 levels by altering T3 synthesis (increase or decrease locally).
• T4 is converted to T3 by deiodination.
• There are three main forms of deiodinase (types exist as a key concept).

5) Effects of Thyroid Hormones

5.1 Core concept

• Thyroid hormones affect virtually every cell → explains wide clinical manifestations with deficiency or excess.

5.2 Mechanism of action (nuclear receptor logic)

• Many actions are mediated by nuclear receptors with preferential affinity for T3.
• T3 receptors are nuclear transcription factors (like steroid hormone receptor family members).
• Key difference vs some steroid receptors:
• Thyroid hormone receptors are in the nucleus (not cytoplasm)
• They may remain bound to DNA even without hormone bound

5.3 Cell entry concept (updated view)

• Thyroid hormones were once considered lipid soluble and easily crossing membranes.
• Now recognised: membrane transport mechanisms exist.

5.4 What happens inside nucleus

1. T3 enters nucleus
2. T3 binds thyroid receptor
3. Receptor forms dimers:
• Homodimer (T3 receptor + T3 receptor)
• Heterodimer (notably with retinoic acid receptor)
4. Dimers interact with DNA → regulate gene expression

5.5 Major metabolic effects (mitochondria + ATPase logic)

In most tissues (exceptions listed below), thyroid hormones increase metabolic rate by:

• Increasing number and size of mitochondria
• Stimulating synthesis of respiratory chain enzymes
• Increasing membrane Na⁺, K⁺-ATPase concentration
• Increasing membrane Na⁺ and K⁺ permeability

Important energy logic:

• 15–40% of a cell’s resting energy expenditure is used to maintain the electrochemical gradient (pumping Na⁺ out in exchange for K⁺).
• Therefore, increasing Na⁺,K⁺-ATPase activity increases resting metabolic rate.

Exceptions where the “stimulate metabolic rate” generalisation is noted as not applying the same way:

• Brain
• Spleen
• Testis

6) Diseases of the Thyroid Gland — Hyperthyroidism Focus

6.1 Definitions: hyperthyroidism vs thyrotoxicosis

• Hyperthyroidism = overactivity of thyroid gland → excessive synthesis of thyroid hormones → accelerated peripheral metabolism.
• Thyrotoxicosis = any state of thyroid hormone excess, including:
• Ingestion of excess thyroid hormone
• Thyroiditis

They’re often used interchangeably, but definition differs as above.

6.2 Epidemiology

• Common disorder:
• ~3% of women
• ~0.5% of men

6.3 Causes vary by age

• In people ≤ 50 years: Graves disease is almost always the cause
• In elderly: toxic nodular goitre is more common

(Signs and symptoms are referenced as summarised in a table.)

7) Graves Disease

7.1 Core identity

• Autoimmune disease characterised by hyperthyroidism due to circulating autoantibodies.
• In some people it is part of a broader autoimmune polyglandular syndrome.

7.2 Targets of autoimmunity (4 thyroid antigens)

B- and T-lymphocyte-mediated autoimmunity directed at:

1. Thyroglobulin
2. Thyroid peroxidase
3. Na⁺–iodide symporter
4. TSH receptor

7.3 Primary autoantigen and why hyperthyroidism happens

• The TSH receptor is the primary autoantigen and drives hyperthyroidism.
• Thyroid is under continuous stimulation by anti–TSH receptor antibodies.
• Pituitary TSH is suppressed due to high thyroid hormones (negative feedback).

7.4 Marker antibodies vs causal role

• Antibodies to:
• Na⁺–iodide symporter
• Thyroglobulin
• Thyroid peroxidase
• seem to have little role in causing hyperthyroidism in Graves and are mainly markers of autoimmune thyroid disease.

7.5 Epidemiology and distinctive clinical features

• Most common cause of hyperthyroidism.
• Female predominance: female : male = 7–8 : 1
• Most clinical features are from the hyperthyroid state, but features virtually unique to Graves:
• Ophthalmopathy
• Dermopathy

7.6 Thyroid examination findings

• Thyroid diffusely enlarged and smooth
• Bruit may be heard due to increased vascularity
• Rare: gynaecomastia

8) Goitre

8.1 Definition

• Goitre = diffuse or nodular enlargement of the thyroid gland.
• Goitre is independent of thyroid function (can occur with normal, high, or low function).

8.2 Age relationship and multinodular goitre

• Thyroid becomes more nodular with increasing age.
• In multinodular goitre:
• Nodules vary in size
• Most are asymptomatic
• Can be:
• Toxic
• Nontoxic

8.3 Toxic multinodular goitre mechanism

• Occurs when multiple autonomous nodules hyperfunction
• Leads to thyrotoxicosis

9) Diagnosis of Hyperthyroidism

9.1 Lab assays used

Assays exist for:

• Serum total T4 and T3
• Free thyroid hormone (free T4/free T3)
• TSH

TRH assays:

• TRH assays are not used

9.2 Typical biochemical pattern in hyperthyroidism

• Total and free T4 and T3 elevated
• TSH suppressed due to negative feedback on hypothalamus and pituitary

9.3 Subclinical hyperthyroidism (definition)

• Free T4 or T3 within reference range
• TSH suppressed

9.4 T3 toxicosis (special subtype)

• Can be when only free T3 is elevated
• Called T3 toxicosis
• May be associated with:
• Toxic multinodular goitre
• Ingestion of T3

9.5 Imaging and functional testing

Structural imaging

• Ultrasound, CT, MRI → show anatomy, size, nodules

Radioactive isotope scanning / uptake (cause differentiation logic)

• Useful to differentiate causes:

1. Graves disease

• Radioactive iodine uptake increased
• Diffuse distribution throughout entire gland

1. Thyroiditis and hyperthyroidism due to excess iodine ingestion

• Poor radioactive uptake

1. Multinodular goitre

• Uptake shows multifocal areas of varying activity
• Helps define functional characteristics of the gland

10) Treatment of Hyperthyroidism

10.1 Treatment goals

• Alleviate symptoms
• Correct the thyrotoxic state (lower thyroid hormone effect/levels)

10.2 Main options to reduce thyroid hormone levels

1. Antithyroid drugs
2. Radioactive iodine
3. Surgery

Each has pros/cons.

10.3 Factors influencing choice of therapy

• Age
• Size of goitre
• Coexisting medical conditions affecting anaesthetic/operative risk

10.4 Drugs that inhibit synthesis/release (two main categories)

Two types of drugs used to inhibit thyroid hormone synthesis and release:

1. Thioamides (thioamides/thiocarbamides)
2. Iodine

(Also other listed agents: perchlorate, lithium, plus symptomatic beta-blockers and glucocorticoids in specific settings.)

10.5 Thioamides (carbimazole, propylthiouracil)

Mechanism

• Inhibit thyroid hormone synthesis by competing with tyrosyl residues of thyroglobulin for oxidised iodine
• Therefore inhibit thyroid peroxidase

Propylthiouracil (PTU) special notes

• Often used in pregnant and lactating women because:
• It binds plasma proteins
• Crosses placenta / enters breast milk in smaller amounts
• Added advantage:
• Reduces hepatic conversion of T4 → T3 (less active → more active)

10.6 Iodine as antithyroid agent

Speed and effect

• Fastest-acting antithyroid agent
• Reduces thyroid hormone synthesis within 3 days
• Mechanism described as presumed autoregulatory:
• Wolff–Chaikoff effect
• Limitation:
• Becomes ineffective with time

10.7 Perchlorate

Action

• Reduces thyroid hormone synthesis (context: especially iodine-related issues)
• “Discharge of iodide excess from thyroid gland” is stated as an advantage in iodine-induced hyperthyroidism.

Why not routinely used

• No longer used routinely because relatively toxic
• Adverse effects include:
• Bone marrow adverse effects (serious)
• In the table: rash, gastric upset, lymphadenopathy, agranulocytosis, aplastic anaemia

10.8 Destruction of thyroid tissue (alternative to drugs)

Methods

• Surgery
• Radioactive iodine isotopes

10.9 Radioactive iodine (iodine-131, 131I)

Key points

• 131I treatment is safe
• Many clinicians use a fixed dose and aim to produce hypothyroidism
• Then treat with oral T4 because it is:
• Cheap
• Effective
• Easy to monitor

Other uses

• 131I also used to treat euthyroid goitres (to avoid surgery)
• Usually reduces thyroid gland volume

Contraindications

• Children
• Pregnant women
• Women who are breastfeeding

Pregnancy timing rule after 131I

• Women of childbearing age should wait at least 4 months after 131I therapy before becoming pregnant

10.10 Surgery

• Usually restricted to large and unsightly goitres
• Especially those not treatable medically or with radioactive iodine

11) Table 17.9 — Pharmacological Treatment of Hyperthyroidism (Rewritten as Logic List)

11.1 Thiocarbamides (e.g., carbimazole, propylthiouracil)

Indications

• Mild thyroid disease + small goitre
• People with eye disease or cardiorespiratory disease
• Pregnant women
• Children

Advantages

• Cheap
• Effective

Disadvantages / adverse effects

• Rash
• Pruritus
• Neutropenia
• Hepatitis
• Pneumonitis

11.2 Beta-adrenoreceptor blocking drugs (e.g., propranolol)

Indications

• Symptomatic relief (especially cardiac symptoms)
• Hyperthyroid storm

Advantages

• Propranolol inhibits conversion of T4 → T3 in liver

Disadvantages / adverse effects

• Asthma
• Heart failure

11.3 Glucocorticoids (e.g., prednisolone)

Indications

• Hyperthyroid storm

Advantages

• Prednisolone inhibits conversion of T4 → T3 in liver

Disadvantages / adverse effects

• Iatrogenic Cushing syndrome

11.4 Iodine (e.g., Lugol’s solution)

Indications

• Hyperthyroid storm
• Before surgery to reduce blood flow

Advantages

• Rapid inhibition of thyroid hormone synthesis (Wolff–Chaikoff effect)

Disadvantages / adverse effects

• Becomes ineffective with time

11.5 Perchlorate

Indication

• Iodine-induced hyperthyroidism

Advantages

• Discharge of iodide excess from thyroid gland

Disadvantages / adverse effects

• Rash
• Gastric upset
• Lymphadenopathy
• Agranulocytosis
• Aplastic anaemia

11.6 Lithium

Indication

• Second-line alternative to thiocarbamides

Advantages

• Inhibits T4 and T3 release

Disadvantages / adverse effects

• Lithium toxicity (tremour, ataxia, coma)
• Polydipsia
• Polyuria

HYPOTHYROIDISM

1) Core idea: What hypothyroidism is

• Hypothyroidism = deficiency of thyroid hormone → a common endocrine disorder.
• Most important global cause (worldwide): iodine deficiency.
• In iodine-sufficient areas: autoimmune thyroid disease (Hashimoto thyroiditis) is the most common cause.
• Thyroid antibodies prevalence: higher in women and increases with age.
• Key immune-mechanism contrast:
• Hashimoto: T-cell–mediated destruction → gland destruction (not stimulation).
• Graves: autoimmune, but tends toward stimulation rather than destruction.

2) Chronic autoimmune thyroiditis (Hashimoto thyroiditis): logic + features

2.1 Similarities to Graves disease (why it can look related)

Hashimoto is similar to Graves in that it:

• Has an autoimmune aetiology
• Occurs with about the same incidence
• Has the same sex bias
• Has a similar peak age of presentation
• Often has a family history of:
• thyroid disease, or
• related autoimmune diseases

2.2 The key difference (the “turning point” mechanism)

• Hashimoto differs because it is associated with cell-mediated destruction of the thyroid gland.

2.3 Why a goitre can happen in Hashimoto (step-by-step logic)

If a goitre is present, it results from two processes together:

1. Diffuse lymphocytic infiltration
• This explains alternative names like chronic lymphocytic thyroiditis.
2. TSH-stimulated hyperplasia of surviving thyroid tissue
• Because thyroid hormones fall → feedback inhibition is lost → TSH rises → stimulates remaining tissue to grow.

2.4 Antibodies associated with Hashimoto (what you expect to find)

• Antibodies against thyroid peroxidase (TPO)
• Antibodies against thyroglobulin

2.5 Hashitoxicosis (why hyperthyroid features can appear)

• Some people get a period of hyperthyroidism called hashitoxicosis.
• Typically:
• milder hyperthyroidism than Graves disease.

3) Diagnosis of primary hypothyroidism (thyroid gland problem)

3.1 The logic

• If the thyroid gland itself fails → T4/T3 fall → negative feedback causes TSH to rise.

3.2 Typical lab pattern (primary hypothyroidism)

• Total T4: low
• Free T4: low
• Total T3: low
• Free T3: low
• TSH: elevated (because hypothalamus + pituitary respond to low hormone levels)

3.3 Subclinical hypothyroidism (definition)

• Free T4 or Free T3: within reference range
• TSH (thyrotrophin): elevated

3.4 Autoimmune lab features + reproductive association

• Typical for autoimmune hypothyroidism:
• Thyroid autoantibodies:
• antimicrosomal (antithyroid microsomal) or anti-TPO
• anti-thyroglobulin
• Clinical association noted:
• Anti-TPO antibodies have been associated with a higher risk of infertility and miscarriage.

4) Diagnosis of secondary and tertiary hypothyroidism (pituitary/hypothalamic problem)

4.1 What’s happening physiologically

• Hypothyroidism can occur due to loss of TSH secretion from:
• Pituitary dysfunction → secondary hypothyroidism
• Hypothalamic dysfunction → tertiary hypothyroidism

4.2 The key diagnostic trap (why TSH alone can mislead)

• In these conditions, TSH does not rise appropriately despite low T4/T3.
• TSH can be:
• normal, or
• slightly elevated
• BUT it is inappropriately low relative to how low T4/T3 are.

4.3 What you must do if secondary/tertiary is suspected

• TSH alone is inadequate.
• You must also measure free T4.

5) Treatment of hypothyroidism (how and why)

5.1 First-line treatment

• Treatment of choice: levothyroxine (synthetic T4)

5.2 Why T4 replacement works well (the logic)

• T4 is chemically stable
• Peripheral tissues convert T4 → T3, so giving T4 supports physiological T3 availability.

5.3 Monitoring and dose adjustment

• Measure TSH after 6 weeks
• Adjust dose in increments of 25–50 micrograms

5.4 Subclinical hypothyroidism: who should be treated (as stated)

• T4 treatment is recommended for people with subclinical hypothyroidism who are positive for antithyroid microsomal antibodies.

5.5 Dose stability and the important exception

• Once the correct dose is established, it tends to remain constant
• Exception: pregnancy
• Need to increase dose by at least 50 micrograms/day
• Goal: maintain normal TSH concentration

6) Altered thyroid function in nonthyroidal illness (euthyroid sick pattern) + the pitfall

6.1 Core idea

• Severe nonthyroidal illness can alter the hypothalamo–pituitary–thyroid axis labs.

6.2 Most common lab pattern described

• TSH: normal or decreased
• Total T4: decreased
• Total T3: markedly decreased

6.3 Why it can be confused with secondary hypothyroidism

• Because TSH may be normal/low with low thyroid hormones.

6.4 The primary abnormality (key mechanism)

• Main issue is decreased peripheral production of T3 from T4.

6.5 Reverse T3 detail

• There may be an increase in reverse T3
• The magnitude correlates with severity of illness

6.6 Recovery phase clue

• During recovery, some people show transient TSH elevation up to 20 mU/L

6.7 Clinical rule about testing

• Do not evaluate thyroid function in critically ill patients unless thyroid dysfunction is strongly suspected.
• If testing is needed:
• TSH alone is insufficient as a screening test.

7) Causes of hypothyroidism: type, frequency, and examples (table turned into logic)

7.1 Primary hypothyroidism (overall: common; ~95%)

Common (95%) causes include:

• Hashimoto’s disease
• Primary (atrophic) hypothyroidism
• Radioiodine therapy
• Surgery of the thyroid gland

7.2 Other primary causes listed under “uncommon (5%)”

Uncommon (5%) causes include:

• Thyroiditis (nonlymphocytic)
• Genetic defect resulting in impaired T4 synthesis
• Antithyroid drugs

7.3 Rare primary causes (<1%)

Rare (<1%) causes include:

• Loss-of-function mutation in the gene encoding the TSH receptor
• Thyroid hormone resistance

7.4 Secondary (pituitary) hypothyroidism (about 1%)

• Frequency: 1%
• Causes:
• Hypopituitarism due to a tumour, surgery, or radiotherapy
• Impaired TSH synthesis

7.5 Tertiary (hypothalamic) hypothyroidism (<1%)

• Frequency: <1%
• Causes:
• Hypothalamic damage due to a tumour, radiotherapy, or trauma

THYROID IN PREGNANCY

1) Changes in normal pregnancy (WHY thyroid tests shift)

A. The 3 drivers (the “3 levers”)

Pregnancy modulates maternal thyroid function mainly via:

1. hCG rises → thyroid stimulation

• hCG has weak TSH-like activity because:
• Structural similarity between hCG and TSH
• Homology between TSH receptor and LH/hCG receptor
• Result (predictable pattern):
• TSH falls in 1st trimester (reciprocal mirror of rising hCG)
• Thyroid gland is mildly stimulated
• Free T4 usually stays normal or slightly high in 1st trimester (despite low TSH)

1. ↑ urinary iodide loss → ↓ plasma inorganic iodine

• Pregnancy ↑ GFR → more iodide excreted
• Plasma inorganic iodine falls
• Thyroid compensates by:
• enlarging
• increasing iodine clearance from plasma
• maintaining euthyroid state
• This is why thyroid size can increase, especially in iodine-deficient regions

1. ↑ T4-binding globulin (TBG) in 1st trimester → more hormone bound

• Estrogen ↑ TBG
• More T4 bound → higher demand for thyroid hormone production to keep free hormone adequate

B. What happens to thyroid hormone measurements (connect the dots)

Total T3/T4

• Rise between ~weeks 6–12
• Then stabilize by mid-gestation
• Reason: ↑ TBG → ↑ bound fraction → total levels look high

Free T3/T4

• Generally within non-pregnant range
• Tend to decrease ~10–15% in late pregnancy

TSH

• Slightly decreases in 1st trimester (hCG effect)
• Then increases later, but stays within normal pregnancy range

C. When hCG causes true biochemical hyperthyroidism (pathologic extension)

Normally hCG stimulation is mainly first half of gestation.

But if hCG is very high, it can push into biochemical hyperthyroidism, e.g.:

• Hyperemesis gravidarum
• Trophoblastic tumours

D. Fetal dependence on maternal thyroid hormone (WHY maternal disease matters)

• There is maternal transfer of thyroid hormone to fetus
• Maternal thyroid provides all thyroid hormone needed for fetal development until fetal thyroid can produce enough
• Fetal TSH and T4 first detectable ~week 10
• If fetus is at risk of thyroid dysfunction → ultrasound surveillance aimed at detecting fetal goitre
• Clinical relevance: fetal goitre can cause airway compromise at delivery

2) Gestational hypothyroidism

A. Causes / clinical picture

• Causes, symptoms, and signs are same as in non-pregnant reproductive-age women

B. Core logic: pregnancy increases hormone requirement

• Because of the “3 levers” above, demand rises
• Therefore women with hypothyroidism need higher levothyroxine to remain euthyroid

C. What happens if untreated

• Hypothyroidism worsens during pregnancy
• Risks increase:
• Fetal loss
• Psychoneurological deficit in the fetus
• Important negative:
• No evidence of increased risk of birth defects simply from a history of maternal hypothyroidism

D. Treatment principle (don’t under-treat)

• If diagnosed in pregnancy → start full replacement T4 immediately, regardless of severity
• Goal: minimize fetal exposure to hypothyroid environment
• In young pregnant women without comorbidity → titrate rapidly

E. Dose changes (pre-existing hypothyroidism)

• If already on T4 before conception:
• Dose commonly needs to ↑ up to ~50% during pregnancy
• Needs close follow-up to keep thyroid hormones optimal

F. Postpartum plan (newly diagnosed during pregnancy)

• If no previous hypothyroidism and diagnosed during pregnancy:
• T4 may be discontinued postpartum
• Reassess TFTs at 5–6 weeks
• Recovery may be delayed (thyroid can remain suppressed for weeks after prolonged therapy)
• Many will remain hypothyroid and ultimately need chronic replacement

3) Neonatal hypothyroidism

A. Causes (examples given)

• Thyroid dysgenesis
• Thyroid hormone resistance
• (Text indicates “a number of causes” including these)

B. Why screening matters (timing → brain outcome)

• Prompt identification + treatment is vital for neuropsychological development
• With screening + immediate replacement:
• Normal IQ at 5–7 years
• If untreated:
• Profound mental and developmental restriction

4) Gestational hyperthyroidism (maternal thyrotoxicosis in pregnancy)

A. Fertility / pregnancy course

• Mild–moderate hyperthyroidism often causes menstrual irregularity
• But fertility not necessarily impaired
• Mild–moderate thyrotoxicosis:
• Not a contraindication to continuing pregnancy
• Pregnancy does not make it harder to control
• Often easier to control during pregnancy
• Relapses tend to occur postpartum

B. Effects (mother vs fetus)

Maternal:

• Premature labour
• Pre-eclampsia
• Heart failure

Fetal:

• Neonatal mortality
• Low birth weight

5) Treatment of hyperthyroidism during pregnancy

A. What you can and can’t use

• Treatment is similar to non-pregnant BUT:
• Radioactive iodine is contraindicated
• Options therefore:
• Antithyroid drugs
• Surgery (when indicated)

B. Antithyroid drugs (thioamides)

• Propylthiouracil (PTU)
• Carbimazole
• (Later section also lists methimazole (MMI) and carbimazole (CMI))

C. Treatment target (why “slightly high free T4”)

• Goal in pregnancy:
• Maintain free T4 at, or slightly above, the upper limit of normal
• Reasoning: avoid fetal hypothyroidism from overtreatment, while keeping mother safe

D. Beta-blockers

• Not recommended for long-term treatment of thyrotoxicosis in pregnancy

E. Breastfeeding on thioamides

• Thioamides transfer into breast milk
• Overall: breastfeeding appears safe in mothers taking thioamides

6) Fetal thyrotoxicosis

A. Main cause (placental antibody transfer)

• Usually from placental transfer of thyroid-stimulating immunoglobulins
• Key trap:
• Antibodies may persist even if mother is ablated or in remission
• Therefore consider fetal thyrotoxicosis in any pregnant woman with past Graves disease, regardless of current maternal thyroid status

B. Clues suggesting the diagnosis

• Persistent fetal tachycardia
• Growth failure
• Increased fetal activity
• Supportive findings:
• Elevated maternal thyroid-stimulating immunoglobulins
• Ultrasound: fetal goitre in a thyrotoxic fetus

C. Why urgent

• Associated with increased fetal morbidity and mortality
• Early diagnosis is crucial

D. Management logic

• Use antithyroid drug therapy directed to fetus (via treating mother)
• Close monitoring is mandatory
• After delivery:
• Baby continues treatment; condition is usually self-limited

7) Endocrine Society practice guidance (thyroid dysfunction in pregnancy & postpartum)

Focus: hypothyroidism (maternal + fetal aspects)

1. Interpreting free T4 during pregnancy

• Be cautious interpreting serum free T4
• Options suggested:
• Use non-pregnant total T4 range (5–12 μg/dl or 50–150 nmol/L) but in 2nd & 3rd trimesters multiply by 1.5
• Or use free T4 index (appears reliable during pregnancy)

1. Avoid overt maternal hypothyroidism

• Known to have serious adverse fetal effects → should be avoided

1. Subclinical hypothyroidism (SCH) definition + treatment logic

• SCH = TSH above trimester-specific upper limit with normal free T4
• May be associated with adverse outcomes (especially in antibody-positive women)
• Retrospective data: T4 improves obstetric outcome
• Unproven effect on long-term neurodevelopment
• Recommendation:
• Treat with T4 if TPO-Ab positive
• Also recommend T4 even if TPO-Ab negative for neuro outcome, but evidence is poor (benefits thought to outweigh risks)

1. Pre-pregnancy target (known hypothyroidism)

• Adjust T4 preconception to achieve TSH ≤ 2.5 mIU/L before pregnancy

1. Early dose increase

• T4 dose often needs increment by 4–6 weeks gestation
• May require ≥30% increase

1. If overt hypothyroidism diagnosed during pregnancy

• Normalize TFTs as rapidly as possible
• Titrate T4 to reach/maintain:
• TSH < 2.5 mIU/L in 1st trimester
• TSH < 3 mIU/L in 2nd & 3rd trimester
• Or trimester-specific TSH ranges
• Monitoring:
• Recheck TFTs within 30–40 days
• Then every 4–6 weeks

1. Euthyroid but thyroid autoimmunity

• If euthyroid early pregnancy but thyroid autoimmunity present → risk of developing hypothyroidism
• Monitor every 4–6 weeks for TSH rise above pregnancy normal

1. After delivery

• Most hypothyroid women should reduce T4 back to pre-pregnancy dose

8) Thyroid nodules in pregnancy (evaluation + decisions)

A. First-line evaluation

• Ultrasound scan + fine-needle aspiration cytology (FNAC)

Ultrasound tells you:

• Nodule size
• Solid vs cystic
• Diffuse thyroid disease
• Previously undetected non-palpable nodules

B. When FNAC is indicated

• Nodules > 1 cm
• Enlarging nodules
• Nodules with palpable cervical lymph nodes

C. What to do with results

• If biopsy adequate and not suspicious:
• Consider TSH suppression with T4 for duration of pregnancy
• If suggestive of malignancy:
• Surgery indicated

9) Thyroid carcinoma in pregnancy (key principles)

• Diagnosis is not an absolute indication for termination
• Pregnancy does not directly alter natural history
• Treatment options limited because radioactive iodine is contraindicated
• Surgery is the main option

10) Postpartum thyroiditis (PPT)

A. What it is + frequency

• Autoimmune thyroid disease occurring within 1 year after delivery
• Reported prevalence: 4–10%

B. Classic time course (important sequence)

• Transient thyrotoxicosis → then hypothyroidism → return to euthyroid by 1 year
• Key rule: thyrotoxicosis always comes before hypothyroidism
• Timing windows:
• Thyrotoxic phase: 2–6 months postpartum
• Hypothyroid phase: 3–12 months postpartum

C. Risk prediction (antibodies in 1st trimester)

• If TPO antibodies or antithyroglobulin antibodies present in 1st trimester:
• 33–50% risk of PPT
• Higher antibody titre → higher risk

D. Outcomes + recurrence

• Spontaneous recovery in ~90%
• Recurrence risk after subsequent pregnancies: up to 25%
• Increased risk of permanent hypothyroidism, especially with high TPO titres → follow-up recommended

E. Why it’s often missed

• Symptoms often subtle and overlap postpartum life:
• fatigue, irritability, weight fluctuations
• Exam finding:
• small painless goitre palpable in ~50%

F. Lab pattern + differentiating from Graves

Thyrotoxic phase:

• High free T4 + suppressed TSH
• Radioisotope uptake (e.g., technetium): low in PPT (helps distinguish from Graves)

Hypothyroid phase:

• High TSH + low T4

11) Autoimmune thyroid disease behavior around pregnancy + antithyroid drug nuances

A. Immune shift pattern

• Autoimmune thyroid disease symptoms often improve during pregnancy
• Postpartum exacerbation is not uncommon (likely immune rebound)

B. Antithyroid drugs (ATDs): which and why

• ATDs listed: PTU, MMI (methimazole), CMI (carbimazole)
• Concern: MMI has controversial association with fetal defects:
• Aplastic cutis / scalp defects
• Choanal atresia
• Oesophageal atresia
• Therefore PTU tends to be first choice (based on this text)

C. PTU safety warning (important counterbalance)

• FDA boxed warning: risk of severe liver injury/acute liver failure, sometimes fatal
• Boxed warning states PTU should be reserved for those who cannot tolerate:
• MMI
• radioactive iodine
• surgery

D. Dosing & monitoring strategy (min effective dose)

• Keep ATD at lowest dose that maintains maternal free T4 in high-normal range
• Monitor monthly:
• weight gain
• pulse rate
• free T4 results
• TSH levels

12) Gestational thyrotoxicosis (NOT intrinsic thyroid disease)

A. Definition + mechanism

• Transient, mild hyperthyroidism early pregnancy
• Due to hCG stimulating TSH receptor (not primary thyroid pathology)
• Higher hCG level or higher hCG activity → higher T4 + suppressed TSH

B. How common + where it happens

• Documented in up to 10–15% of pregnant women
• Common settings:
• Multiple gestations
• Hyperemesis gravidarum
• Hydatidiform mole
• Familial gestational thyrotoxicosis (TSH receptor mutation)

C. Typical symptoms + natural course

• Usually mild:
• nausea ± vomiting
• Resolves spontaneously by ~20 weeks
• T4 normalizes by ~14–20 weeks

D. Severe form: transient hyperthyroidism of hyperemesis gravidarum

• Features:
• severe nausea/vomiting
• dehydration
• weight loss
• ketonuria
• May need:
• hospitalisation
• parenteral nutrition (as written)

E. Key management logic

• Distinguishing from Graves can be challenging
• Antithyroid drugs NOT indicated because it subsides with pregnancy progression
• Note: In some patients, TSH can remain suppressed even after T4 normalizes

Endocrine pancreas — Logic-based notes (section by section, zero omissions)

1) Endocrine pancreas: what it does (big picture)

• Pancreas has 2 jobs
• Exocrine (digestive) function
• Secretes enzymes into duodenum to break down:
• carbohydrates, fats, proteins, acids
• Also secretes bicarbonate (HCO3−) to neutralise stomach acid in the duodenum
• Endocrine (hormonal) function
• Endocrine tissue secretes these hormones:
• insulin
• glucagon
• somatostatin
• gastrin
• vasoactive intestinal peptide (VIP)
• pancreatic polypeptide

2) Insulin

2.1 Structure + synthesis pathway (logic flow: gene → peptide processing → mature insulin)

• Insulin = protein hormone
• Molecular weight ~ 6000 Dalton
• Two chains held together by disulphide bonds
• Synthesis steps
1. Insulin mRNA translated into preproinsulin (single-chain precursor)
2. During insertion into endoplasmic reticulum (ER):
• Signal peptide removed → becomes proinsulin
3. Proinsulin has 3 domains
• Amino-terminal B chain
• Carboxy-terminal A chain
• Middle connecting peptide = C peptide
4. In ER, proinsulin exposed to specific endopeptidases
• These excise the C peptide
• → generates mature insulin
• Secretion
• When beta cell is appropriately stimulated
• Insulin released by exocytosis
• Then diffuses into islet capillary blood

2.2 Insulin secretion after oral glucose load (logic: early neural → late glucose-driven)

• After oral glucose load, insulin secretion has 2 components:
• Early response (30 minutes) → due to neuronal stimulation
• Late response (120 minutes) → mainly due to elevated blood glucose concentration

2.3 How glucose triggers insulin release (logic: glucose in → depolarise → Ca2+ in → granule exocytosis)

• Glucose enters beta cell
• Via facilitated diffusion through a glucose transporter
• This leads to:
• Membrane depolarisation
• Influx of extracellular Ca2+
• ↑ intracellular Ca2+
• This rise is a primary trigger for exocytosis of insulin-containing secretory granules
• Also:
• Increased glucose inside beta cells activates Ca2+-independent pathways
• These also participate in insulin secretion

2.4 Insulin receptor (logic: membrane receptor → kinase signaling)

• Insulin receptor = tyrosine kinase embedded in plasma membrane
• Structure:
• 2 alpha subunits + 2 beta subunits
• Subunits linked by disulphide bonds

2.5 Major target tissues (logic: insulin is anabolic where fuel is stored/used)

• Main targets for anabolic actions:
• liver
• adipose tissue
• muscle

2.6 Metabolic actions (logic: store fuel + stop fuel breakdown)

• In liver
• Promotes glycogen synthesis by:
• stimulating glycogen synthetase
• inhibiting glycogen phosphorylase
• In muscle and fat
• Induces rapid glucose uptake
• Consequences:
• muscle converts glucose → glycogen
• adipose tissue converts glucose → fatty acids → stored as triglyceride
• Protein metabolism
• Stimulates uptake of amino acids into muscle
• Anti-mobilisation effects (insulin blocks fuel release)
• Inhibits:
• breakdown of glycogen in liver
• release of amino acids from muscle
• release of free fatty acids from adipose tissue
• Clinical logic point
• This helps explain weight loss in diabetes despite normal or increased appetite:
• because without effective insulin action, you lose the “store + stop breakdown” control.

3) Glucagon

3.1 Structure + synthesis (logic: prohormone → processing in alpha cells)

• Glucagon = linear peptide, 29 amino acids
• Initially synthesised as proglucagon
• Proteolytically processed within alpha cells of pancreatic islets → yields glucagon

3.2 When glucagon is secreted (logic: “low sugar / need fuel” signals)

• Secreted in response to:
• hypoglycaemia
• also stimulated by:
• elevated serum amino acids
• exercise

3.3 What inhibits glucagon secretion (logic: “high sugar / insulin present / somatostatin brake”)

• Inhibited by:
• high blood glucose
• either direct effect on alpha cells
• or indirectly via insulin from beta cells
• somatostatin

3.4 Actions (counter-regulatory to insulin; mobilisation mode)

• Glucagon acts opposite to insulin:
• promotes mobilisation of fuels, especially glucose
• Primary target = liver
• stimulates:
• breakdown of glycogen → glucose
• gluconeogenesis (glucose from amino acids)
• Also stimulates:
• release of free fatty acids from adipose tissue
• Glucagon is:
• hyperglycaemic
• ketogenic
• Key governing concept:
• The molar ratio of insulin : glucagon in portal blood
• largely governs the metabolic state of the liver

4) Somatostatin

4.1 Where it comes from (logic: widespread “brake hormone”)

• Secreted by many tissues, including:
• pancreas
• gastrointestinal tract
• regions of CNS outside hypothalamus

4.2 Forms + processing (logic: one precursor → 2 active lengths)

• Two forms:
• somatostatin 14
• somatostatin 28
• (numbers reflect amino acid length)
• Both generated by proteolytic cleavage of prosomatostatin
• Predominant sources:
• Somatostatin 14: mainly produced in nervous system
• Somatostatin 28: intestine secretes mostly this form

4.3 Potency differences (important exam logic)

• Two forms have different biological potencies
• Somatostatin 28
• ~ 10× more potent than somatostatin 14 at inhibiting growth hormone secretion
• but less potent than somatostatin 14 at inhibiting glucagon release

4.4 Receptors (logic: multiple GPCRs; most don’t differentiate)

• Five somatostatin receptors identified
• All are G-protein–coupled receptor superfamily
• Four of five receptors do not differentiate between somatostatin 14 and 28

4.5 How it acts (endocrine + paracrine)

• Acts via:
• endocrine pathways
• paracrine pathways
• General role:
• inhibits secretion of many other hormones
• including growth hormone from pituitary

4.6 Pancreatic actions (mainly paracrine brake inside islets)

• In pancreas, acts primarily paracrine to inhibit:
• insulin secretion
• glucagon secretion
• Also suppresses pancreatic exocrine secretions by inhibiting:
• CCK-stimulated enzyme secretion
• secretin-stimulated bicarbonate secretion

4.7 GI actions (logic: slows digestion + absorption)

• Inhibits secretion of many GI hormones
• Also:
• suppresses gastric acid and pepsin
• lowers gastric emptying rate
• reduces smooth muscle contractions and blood flow in intestine
• Net effect:
• decreases rate of nutrient absorption

5) Vasoactive intestinal peptide (VIP)

5.1 What it is + where produced

• VIP = peptide hormone, 28 amino acids
• Produced in many areas including:
• gut
• pancreas
• suprachiasmatic nuclei of hypothalamus (brain)

5.2 Digestive system roles (logic: secretion + vasodilation + pancreas bicarbonate + acid inhibition)

• Stimulates:
• H2O and electrolyte secretion
• Causes:
• dilatation of peripheral blood vessels
• Stimulates:
• pancreatic bicarbonate secretion
• Inhibits:
• gastrin-stimulated gastric acid secretion

5.3 Receptors

• Acts via 2 VIP-specific receptors:
• VPAC1
• VPAC2

6) Gastrin

6.1 Synthesis + peptide family (logic: preprohormone → multiple lengths)

• Gastrin = linear peptide
• Synthesised as a preprohormone
• Cleaved to form a family of peptides
• Predominant circulating form:
• gastrin-34 (“big gastrin”)
• Even smallest peptide has biological activity:
• gastrin-14 (“minigastrin”)
• Core “minimum active” region:
• Full bioactivity preserved in 5 carboxy-terminal amino acids
• called pentagastrin

6.2 Where it is made

• Synthesised in G cells
• G cells located in gastric pits
• Mainly in antrum of stomach

6.3 Receptors (and shared binding with CCK)

• Gastrin binds receptors mainly on:
• parietal cells
• enterochromaffin-like (ECL) cells
• These receptors also bind cholecystokinin (CCK)
• Named:
• gastrin/CCK type B receptors
• Receptor family:
• G-protein-coupled receptors

6.4 Actions (logic: acid + mucosal growth)

• Major physiological regulator of:
• gastric acid secretion
• Also has:
• growth-promoting influence on gastric mucosa

6.5 Control of secretion (stimulus vs inhibition)

• Primary stimulus:
• presence of certain foodstuffs in gastric lumen, especially:
• peptides
• certain amino acids
• Ca2+
• Inhibited when:
• luminal pH becomes very low

Endocrine diseases of the pancreas

7) Diabetes mellitus

7.1 Definition (logic: hyperglycaemia because insulin secretion/action fails)

• Group of metabolic diseases characterised by hyperglycaemia
• Due to defects in:
• insulin secretion
• insulin action
• or both

7.2 Diagnostic criteria (symptoms + one of the thresholds)

Diagnosis based on symptom history plus meeting one:

• Random venous plasma glucose ≥ 11.1 mmol/L
• Fasting plasma glucose ≥ 7.0 mmol/L
• 2-hour plasma glucose ≥ 11.1 mmol/L after 75 g anhydrous glucose in OGTT

Important logic rule (no symptoms)

• If no symptoms, do not diagnose from a single glucose test
• Need at least one additional glucose test on another day
• sample can be random, fasting, or 2 hours after glucose load
• Diagnosis should never be based only on glycosuria

7.3 HbA1c for diagnosis (WHO recommendation)

• In January 2011, WHO recommended HbA1c can be used as an alternative to glucose measures to diagnose type 2 diabetes in non-pregnant adults
• HbA1c ≥ 6.5% (48 mmol/mol) indicates type 2 diabetes
• There is no fixed point for “pre-diabetes”
• WHO statement:
• increasing HbA1c up to the 6.5% cut-off = increased risk
• risk is a continuum across sub-diabetic HbA1c levels

7.4 Normal vs impaired fasting / impaired tolerance thresholds

• Normal fasting blood glucose generally:
• < 6 mmol/L
• Impaired fasting glucose:
• 6.0 to 7.0 mmol/L
• Impaired glucose tolerance (2h after 75 g oral glucose):
• 7.8 to 11.1 mmol/L

8) Type 1 diabetes mellitus

8.1 Pathophysiology (logic: T-cell autoimmune destruction of beta cells)

• Considered a T-lymphocyte dependent autoimmune disease
• Characterised by:
• infiltration and destruction of beta cells in islets of Langerhans

8.2 Genetics + twin studies (logic: genetic predisposition but not enough alone)

• Twin studies show major genetic element
• But in fewer than half of identical twin pairs:
• if one has disease, the other also develops it

8.3 Autoimmunity + associated diseases

• Autoimmunity considered major factor in pathophysiology
• Increased prevalence in people with other autoimmune diseases:
• Graves disease
• Hashimoto thyroiditis
• Addison’s disease

8.4 Antibodies (what’s common and what they target)

• About 85% have circulating islet cell antibodies
• Majority have detectable anti-insulin antibodies before receiving insulin therapy
• Most islet cell antibodies are directed against:
• glutamic acid decarboxylase (GAD) within pancreatic beta cells

8.5 Environmental triggers hypothesised

• Viruses (examples given):
• mumps
• rubella
• Coxsackie B4
• Also:
• toxic chemicals
• cytotoxins
• exposure to cow’s milk in infancy

8.6 Epidemiology

• Predominantly a disease of white populations
• Tends to develop after age 20
• Overall frequency: equal in men and women
• Incidence increases:
• around puberty
• before starting school

8.7 Treatment + long-term management

• Requires lifelong insulin therapy for hyperglycaemia control
• Most require two or more injections daily
• doses adjusted based on self-monitoring of blood glucose
• Long-term management: multidisciplinary
• physicians, nurses, dietitians, selected specialists
• Goal:
• keep glucose normal or near-normal
• Insulin types differ by:
• onset
• duration
• Tight control helps prevent:
• short-term effects (e.g. diabetic ketoacidosis)
• long-term effects (complications of eye, kidney, cardiovascular system)

8.8 Pancreatic transplantation

• Possible in some referral centres
• Most commonly performed with simultaneous kidney transplantation
• for end-stage renal disease (ESRD)

9) Type 2 diabetes mellitus

9.1 Core features (must all be understood together)

• Characterised by:
• hyperglycaemia
• insulin resistance
• relative impairment of insulin secretion

9.2 Obesity link + requirement for both problems

• Common disorder; prevalence rises markedly with increasing obesity
• For type 2 DM to develop:
• both insulin deficiency and insulin resistance defects must coexist
• All overweight individuals have insulin resistance
• but only those who cannot increase beta cell insulin production develop diabetes
• About 90% who develop type 2 DM are obese

9.3 Why hyperglycaemia worsens (glucagon not suppressed)

• Relative insulin deficiency from damaged beta cells → lack of glucagon suppression
• This further contributes to hyperglycaemia

9.4 DKA tendency

• People with type 2 DM retain ability to secrete some endogenous insulin
• Generally do not develop diabetic ketoacidosis

9.5 Metabolic syndrome cluster

• Often accompanied by:
• hypertension
• dyslipidaemia
• high LDL
• low HDL
• This cluster = metabolic syndrome
• Associated with increased risk of cardiovascular disease

10) Treatment of diabetes mellitus (overall strategy)

10.1 Complications: two big buckets

• Microvascular
• retinopathy
• nephropathy
• neuropathy
• Macrovascular
• atherosclerotic disease of coronary, carotid, femoral arteries

10.2 Why control matters (logic: duration + degree of control)

• Complications largely related to:
• duration of disease
• degree of blood sugar control
• Therefore, strong focus on controlling blood glucose

10.3 Lifestyle foundations

• Important in all forms:
• sensible diet
• weight control
• exercise
• Also manage:
• dyslipidaemia
• blood pressure

10.4 Dietary modification (healthy eating diet structure)

• Fundamental to long-term treatment
• “Healthy eating diet”:
• >55% carbohydrate
• 10–15% protein
• <30% fat
• and <10% saturates
• Usually no further modification needed except:
• reduce sources of simple sugars
• <25 g/day added sucrose
• replace with complex carbohydrates

10.5 Monitoring control: HbA1c targets and progression reality

• Glycaemic control judged by HbA1c
• Optimal HbA1c for a person with diabetes:
• 6.5% to 7.0%
• Many type 2 diabetics have inadequate control
• Monotherapy fails by end of 9 years in 75%
• Therefore recommended:
• early aggressive combination therapy
• do not allow HbA1c to go above 7.8%

10.6 EASD/ADA position: 7 key points

1. Individualised glycaemic targets and glucose-lowering therapies
2. Diet, exercise, education as foundation
3. Metformin optimal first-line unless contraindicated
4. After metformin: 1 or 2 additional oral/injectable agents, aim to minimise adverse effects if possible
5. Ultimately insulin therapy alone or with other agents if needed
6. Decisions involve patient, focusing preferences/needs/values
7. Major focus on comprehensive cardiovascular risk reduction

10.7 Pharmacotherapy classes listed

• Biguanides
• Sulphonylureas
• Meglitinide derivatives
• Alpha-glucosidase inhibitors
• Thiazolidinediones (TZDs)
• GLP-1 agonists
• DPP-4 inhibitors
• Selective SGLT-2 inhibitors
• Insulins

11) Drug classes (mechanisms + key clinical points)

11.1 Biguanide (Metformin)

• Reduces hepatic glucose release
• First-line in overweight and non-overweight people
• Lowers:
• basal glucose
• postprandial glucose
• Reduces cardiovascular outcomes in obese individuals
• Adverse effects:
• gastrointestinal
• Rarely causes:
• hypoglycaemia
• Contraindicated in:
• impaired renal function
• Also should not be used within 48 hours of:
• intravenous iodinated contrast medium

11.2 Sulphonylureas

• Stimulate insulin release from pancreatic beta cells
• Usually reduce:
• HbA1c by 1–2%
• blood glucose by about 20%
• Effective but associated with:
• weight gain
• hypoglycaemia
• accelerated beta-cell exhaustion

11.3 Meglitinides

• Much more short-acting insulin secretagogues than sulphonylureas
• Preprandial dosing
• more physiological insulin release
• less hypoglycaemia risk
• Monotherapy efficacy similar to sulphonylureas

11.4 Alpha-glucosidase inhibitors

• Prolong absorption of carbohydrates → prevents postprandial glucose surges
• Major limiting issue:
• flatulence
• Dosing:
• titrate slowly to reduce GI intolerance
• Effect:
• modest glycaemic control
• mainly affects postprandial excursions

11.5 Thiazolidinediones (TZDs)

• Reduce insulin resistance in periphery:
• sensitise muscle and fat to insulin
• Also small effect in liver
• Mechanism:
• activate PPAR gamma
• nuclear transcription factor important in:
• fat cell differentiation
• fatty acid metabolism
• May have:
• beta-cell preservation properties
• Efficacy:
• moderate
• Use:
• monotherapy or combination
• Weight:
• modest weight gain
• Time to maximal effect:
• 12–16 weeks
• Side effects:
• fluid retention
• worsening heart failure
• increased risk of fractures
• bladder cancer
• Regulatory notes:
• Rosiglitazone banned in Europe and restricted in USA (increased cardiovascular morbidity)
• Pioglitazone banned in France; black-box warnings in USA (bladder cancer)

12) Incretins (gut factors that boost glucose-stimulated insulin)

12.1 Definition

• Incretins = gut-derived factors that increase glucose-stimulated insulin secretion

12.2 Two incretin hormones listed

• GLP-1
• produced in ileum and colon
• Gastric inhibitory peptide
• produced in jejunum

12.3 GLP-1 analogues (GLP-1 agonists)

• Mechanism: mimic endogenous GLP-1
• stimulate glucose-dependent insulin release
• contrasted with oral secretagogues that may cause non–glucose-dependent insulin release and hypoglycaemia
• reduce glucagon
• slow gastric emptying
• Route:
• subcutaneous injections

12.4 DPP-4 inhibitors

• Block action of DPP-4
• enzyme that destroys incretin
• Effects:
• increase insulin release
• decrease glucagon
• glucose-dependent manner
• GLP-1 action can be enhanced by oral DPP-4 inhibitor
• Dosing:
• once daily, oral
• Weight:
• weight neutral
• Use:
• monotherapy or combination with:
• other oral hypoglycaemics
• insulin treatment

12.5 SGLT-2 inhibitors

• Reduce glucose reabsorption in proximal renal tubules
• Lower renal threshold for glucose
• Increase urinary glucose excretion
• Indications:
• adjunct to diet and exercise to improve glycaemic control in type 2 DM
• monotherapy, initial therapy with metformin, or add-on to other oral agents and insulin

13) Insulins (clinical use and regimens)

13.1 Starting doses (Type 1)

• Newly diagnosed type 1:
• total daily insulin dose 0.2–0.4 U/kg
• Ultimately most require:
• 0.6–0.7 U/kg daily
• Adolescents often need more, especially during puberty

13.2 Type 2 progression to insulin

• About 1 in 3 people with type 2 DM will require insulin at some stage

13.3 Indications for insulin therapy in type 2 DM

• Symptoms of hyperglycaemia:
• polyuria
• thirst
• recurrent fungal infections
• bacterial infections
• Pregnancy or planning pregnancy
• Oral hypoglycaemics not tolerated or contraindicated
• Weight loss
• Painful neuropathy
• Foot ulceration and infection

13.4 Insulin types by onset/peak/duration

• Rapid-acting
• starts within a few minutes
• lasts a couple of hours
• Regular/short-acting
• takes about 30 minutes to work fully
• lasts 3–6 hours
• Intermediate-acting
• takes 2–4 hours to work fully
• effects last up to 18 hours
• Long-acting
• takes 6–10 hours to reach peak levels
• can keep working 24 hours

13.5 Two schemes for insulin treatment (basal + bolus logic)

• Scheme 1: Basal insulin = ~half total daily dose
• either:
• once daily long-acting, or
• twice daily intermediate-acting (isophane)
• Long-acting can be given:
• at bedtime or in the morning
• Scheme 2: Remaining dose = short/rapid-acting before meals
• “sliding scale insulin therapy”
• Pre-meal dose determined by:
• carbohydrate content of meal
• blood glucose level
• activity level

13.6 Treatment targets (widely accepted)

• Fasting blood sugar: < 7 mmol/L
• HbA1c: ≤ 6.5%
• Systolic BP: < 130 mmHg
• Diastolic BP: < 80 mmHg
• Total cholesterol: < 4 mmol/L
• HDL cholesterol: > 1 mmol/L
• LDL cholesterol: < 2 mmol/L
• Triglycerides: < 1.5 mmol/L

13.7 Insulin pumps (continuous subcutaneous insulin infusion)

Recommended possible treatment for adults and children ≥12 years with type 1 DM if:

• attempts to reach target HbA1c with multiple daily injections cause disabling hypoglycaemia, OR
• HbA1c remains high (8.5% or above) with multiple daily injections including long-acting analogues, despite careful management by person/carer

14) Endocrine tumours of the pancreas (APUD tumours)

14.1 APUD concept

• Cells in pancreatic endocrine neoplasms termed APUD cells
• meaning: amine precursor uptake and decarboxylation
• Reasons for name:
• high amine content
• capable of amine precursor uptake
• contain an amino acid decarboxylase

14.2 Functional vs nonfunctional (logic: hormone excess vs mass effect)

• Most clinically discovered pancreatic endocrine neoplasms are functional apudomas
• Named after predominant secreted hormone:
• insulinoma
• gastrinoma (Zollinger–Ellison syndrome)
• glucagonoma
• VIPoma (Verner–Morrison syndrome)
• somatostatinoma
• Functional tumours: clinical features reflect physiological derangements from excess hormone action
• Nonfunctional tumours:
• present later
• symptoms due to mass effect

14.3 Investigation principle (logic: “inappropriate hormone level for the situation”)

• Investigation largely = demonstrate circulating hormone concentrations are inappropriate to the clinical situation

14.4 Treatment

• These tumours usually:
• grow slowly
• have relatively low metastatic potential
• Definitive treatment:
• surgical removal
• Medical symptom control:
• somatostatin analogues may control symptoms if tumour expresses somatostatin receptors
• proton pump inhibitors major role for symptomatic relief in gastrinomas
• Liver metastases options:
• embolisation
• radiofrequency ablation

Endocrine Pancreas & Pregnancy — Logic-Based Notes (Section-by-Section, Zero Omission)

1) Glucose Metabolism During Pregnancy

A) What changes, and how early?

• Pregnancy changes basal and postprandial glucose metabolism as early as the end of the 1st trimester.

B) Nonpregnant baseline (reference point)

• In the nonpregnant state, the liver is the predominant source of endogenous glucose production.

C) Fasting (basal) state in normal pregnancy — the “paradox” logic

Observed in normal pregnancy (especially late pregnancy):

• Reduced fasting plasma glucose
• Increased fasting insulin

Why? (logic)

• Presumably due to increased glucose uptake by the fetal–placental unit.

But simultaneously:

• Maternal hepatic glucose production is increased
• This suggests:
• Reduced hepatic insulin sensitivity, or
• Hepatic insulin resistance
• Purpose (logic): to increase glucose availability to the fetus during fasting.

D) Postprandial state in normal pregnancy

• Postprandial glucose values are slightly elevated
• Occurs with maternal postprandial hyperinsulinaemia
• This is especially seen in the 2nd and 3rd trimesters.

E) Why does insulin sensitivity fall in pregnancy?

• The physiological factors are not fully known.
• Implicated factors (levels elevated in maternal circulation):
• Hormones: human placental lactogen, progesterone, prolactin, cortisol
• Cytokines: tumour necrosis factor alpha (TNF-α)

Extra TNF-α logic

• Increased TNF-α is associated with decreased insulin sensitivity in:
• Obesity
• Ageing
• Sepsis

F) Insulin levels across gestation + lean vs obese logic

• In normal pregnancy, there are progressive increases in insulin concentration with advancing gestation.
• These increases are more pronounced in lean women than in obese women because:
• Lean women start pregnancy with better insulin sensitivity.
• Lean women have a greater total decrease in insulin sensitivity than obese women with normal glucose tolerance.

G) Compensation logic: secretion vs resistance timing

• Increased insulin secretion in pregnancy represents compensation for progressive insulin resistance.
• Key timing detail:
• Insulin secretion increases by as much as 50% early in the 2nd trimester
• This occurs before insulin resistance of pregnancy becomes manifest.
• Therefore:
• Pregnancy may exert a primary effect increasing insulin secretion that is independent of insulin resistance.

2) Lipid Metabolism During Pregnancy

A) Overall changes

• Significant alterations occur in lipid metabolism during pregnancy.

B) Fat gain in normal pregnancy

• Women who are not obese gain ~3.5 kg of fat during normal pregnancy.
• There is wide variation within and between ethnic and racial groups.

C) Distribution pattern across gestation

• Early gestation: subcutaneous fat mass increases, primarily centrally distributed.
• Late 3rd trimester: increase in both:
• Preperitoneal fat
• Subcutaneous fat
• Increase in visceral fat may relate to the decrease in insulin sensitivity in late gestation.

D) Lean vs obese

• Lipid metabolism differs between lean and obese women with normal glucose metabolism.

E) Lipid profile changes (numbers you must keep)

• Triglycerides: increase 2- to 4-fold
• Total cholesterol: increases 25–50%
• LDL cholesterol: 50% increase
• HDL cholesterol:
• 30% increase by midgestation
• followed by a slight decrease at term
• Free fatty acids: increase in late pregnancy

3) Fetal Endocrine Pancreas

A) Development timing

• The fetal pancreas appears during the 4th week of fetal life.

B) Cell development order (high-yield sequence)

• Alpha cells (glucagon) and delta cells (somatostatin) develop before differentiation of beta cells.

C) Hormone concentrations across fetal age

• Human pancreatic insulin and glucagon concentrations:
• Increase with advancing fetal age
• Are higher than adult pancreas concentrations

D) Maternal diabetes effect on fetal islets

• In maternal diabetes mellitus:
• Fetal islet cells undergo hypertrophy
• Rate of insulin secretion increases

4) Diabetes in Pregnancy (Epidemiology + Big Picture)

A) How common?

• Abnormal maternal glucose regulation occurs in 3–10% of pregnancies.

B) Why increasing worldwide?

• Prevalence of diabetes mellitus among women of childbearing age is increasing due to:
• More sedentary lifestyles
• Changes in diet
• Continued immigration from high-risk populations
• Epidemic of childhood and adolescent obesity

C) Contribution of GDM

• Gestational diabetes mellitus (GDM) accounts for 90% of diabetes in pregnancy.

5) Gestational Diabetes Mellitus (GDM) — Definition + Core Physiology

A) Definition

• GDM = carbohydrate intolerance first identified during pregnancy.

B) Key metabolic characteristics (as described)

1. Fasting glucose rises
• Women with GDM have increased fasting glucose.
• In obese women with GDM, fasting insulin also rises and is greater than in women without GDM.
• Logic: glucose is high despite higher insulin → imbalance between:
• insulin required for tissue regulation vs
• beta-cell ability to meet requirements
2. Insulin resistance increases early
• Increased insulin resistance from before conception through early pregnancy (weeks 12–14)
• especially in women with reduced insulin sensitivity before conception.
3. Failure to suppress hepatic free fatty acid production
• There is failure to suppress the hepatic production of free fatty acids.

C) Insulin signalling defects (what’s unique in GDM)

• In normal pregnancy: insulin signalling changes occur postreceptor.
• In GDM: defects occur not only postreceptor, but also at the receptor level:
• Tyrosine phosphorylation of the insulin-receptor beta subunit is impaired
• This defect is not found in pregnant or nonpregnant women with normal glucose tolerance.
• Result: 25% decrease in glucose transport activity
• These receptor defects may contribute to:
• Pathogenesis of GDM
• Increased risk of type 2 diabetes later in life

D) Adiponectin + TNF-α balance (insulin sensitivity logic)

• Women with GDM have decreased serum adiponectin
• correlates with decreased insulin sensitivity and impaired glucose disposal
• Adiponectin facts:
• Secreted from adipose tissue
• Serum concentrations negatively associated with:
• obesity
• hyperinsulinaemia
• insulin resistance
• Opposing effects:
• Adiponectin increases insulin sensitivity
• TNF-α reduces insulin sensitivity

E) “Why GDM happens” — beta-cell inadequacy on chronic resistance background

• GDM results from inadequate insulin secretion in women with chronic insulin resistance → related to type 2 diabetes.
• Beta-cell defects in GDM may mirror the spectrum seen in nonpregnant diabetes.
• Quantitative defect:
• Women with GDM have 30–70% decrease in beta-cell function relative to women who maintain normal glucose tolerance.
• Key logic:
• Insulin secretion increases in GDM pregnancy but not enough.
• Pregnancy acts as a “stress test” that reveals chronic metabolic abnormalities that predate pregnancy, detected because pregnancy triggers first glucose tolerance evaluation in otherwise healthy young women.

F) Future diabetes risk after GDM

• Risk of type 2 diabetes after GDM: 20–50%.

G) Lipids in GDM (compared with normal pregnancy)

• Women with GDM (like pregestational type 2 diabetes) have:
• Higher triglycerides
• Decreased HDL compared with pregnant women with normal glucose tolerance.

6) Screening & Diagnosis of GDM

A) Prevalence in evaluated pregnancies

• GDM is found in 1–4% of evaluated pregnancies.

B) Why diagnosis is difficult

• More than one diagnostic test
• No agreed gold standard
• Several threshold criteria
• No agreement on which criteria best identify women at risk of poor outcomes

C) Screening approaches (general framework)

• Screening methods generally include:
• Risk factor assessment
• Laboratory glucose measurement

D) Risk factors used in assessment (explicit list)

• Maternal age
• Ethnicity
• Obesity
• Gestational weight gain
• Suspected macrosomia
• Polyhydramnios
• Glycosuria

Also include histories:

• Family history of diabetes
• Previous GDM
• Delivery of a macrosomic infant
• Stillbirth
• Neonatal death
• Congenital anomaly

Risk factor screening can also:

• Identify low-risk women in whom laboratory testing can be avoided.

E) Timing

• Risk assessment: first prenatal visit
• Laboratory testing: usually weeks 24–28

F) “Overt diabetes” thresholds that bypass challenge testing

• Fasting plasma glucose > 7.0 mmol/L OR casual plasma glucose > 11.1 mmol/L
• If confirmed on a subsequent day → no need for glucose challenge

G) If not overt diabetes: 2 main strategies

1. One-step approach
• Diagnostic OGTT without prior screening
• May be cost-effective in high-risk individuals/populations
2. Two-step approach
• Step 1: measure plasma/serum glucose 1 hour after a 50 g oral glucose load (glucose challenge test)
• Step 2: diagnostic OGTT only for women exceeding threshold

Two-step cutoffs and detection yield

• Threshold 7.8 mmol/L identifies ~80% of women with GDM
• Cutoff 7.2 mmol/L increases yield to 90%

H) OGTT details

• Diagnosis is based on an OGTT.
• Glucose load can be 100 g or 75 g.
• 75 g OGTT is not as well validated for detection of at-risk infants or mothers as 100 g OGTT.

7) Maternal Morbidity Associated With Diabetes During Pregnancy

A) Microvascular complications can worsen

• Women with diabetic microvascular complications at start of pregnancy may deteriorate, partly due to rapid induction of glycaemic control in early pregnancy.

B) Eye (retinopathy) monitoring

• Recommendations include baseline ophthalmology referral with follow-up according to degree of retinopathy.

C) Kidney (nephropathy)

• Underlying nephropathy may show varying degrees of renal deterioration.
• Proteinuria increases.
• Generally pregnancy does not cause progression to end-stage renal disease.

D) Hypertension and pre-eclampsia

• Chronic hypertension complicates ~1 in 10 pregnancies in women with diabetes.
• Pre-eclampsia is more frequent among women with diabetes.

E) After pregnancy

• Women with GDM have increased risk of developing diabetes (usually type 2).
• Obesity and other insulin-resistance factors enhance risk after GDM.

8) Fetal Morbidity Associated With Diabetes During Pregnancy

A) Miscarriage risk relates to pre-pregnancy glycaemic control

• Strong association between pre-pregnancy glycaemic control and miscarriage rate.
• Longstanding (>10 years) and poorly controlled (HbA1c > 11%) diabetes → miscarriage rate up to 44%.

B) Congenital anomalies (numbers + timing logic)

• Major birth defects baseline: 1–2% general population.
• Overt diabetes + suboptimal control before conception:
• Structural anomaly risk 4- to 8-fold higher.
• Two thirds of anomalies involve:
• Cardiovascular system
• Central nervous system
• Periconceptional control is the main determinant.
• Critical window:
• Birth defects occur 3–6 weeks after conception
• Therefore intervention must start well before pregnancy begins.

C) Mechanism of macrosomia: maternal → fetal hyperglycaemia → fetal hyperinsulinaemia

• Inadequate maternal pancreatic insulin response → maternal hyperglycaemia → fetal hyperglycaemia.
• Typically: recurrent postprandial hyperglycaemic episodes.
• These episodes cause:
• Accelerated fetal growth
• Episodic fetal hyperinsulinaemia
• Fetal hyperinsulinaemia promotes nutrient storage → macrosomia

D) Macrosomia frequency + modifiers + pattern

• Macrosomia occurs in 15–45% of diabetic pregnancies (about 4-fold increase vs normoglycaemic pregnancies).
• Maternal obesity (common in type 2 diabetes) significantly accelerates risk of large-for-gestational-age infants.
• Unique overgrowth pattern:
• Central deposition of subcutaneous fat in:
• Abdominal area
• Interscapular area
• Neonatal morbidity rates are excessive among macrosomic newborns.

E) Fetal hypoxia → catecholamines → downstream effects

• Converting excess glucose to fat increases fetal energy expenditure → depletes fetal O2.
• Fetal hypoxia episodes → surges in adrenal catecholamines → cause:
• Hypertension
• Cardiac remodelling and hypertrophy
• Stimulation of erythropoietin
• Red cell hyperplasia
• Increased haematocrit

Polycythaemia

• Defined here as haematocrit > 65%
• Occurs in 5–10% of newborns of diabetic mothers
• Related to glycaemic control; mediated by decreased fetal O2 tension
• High haematocrit → vascular sludging, poor circulation → postnatal hyperbilirubinaemia

F) Growth restriction can also occur (especially type 1 + vasculopathy)

• Growth restriction occurs with significant frequency in pre-existing type 1 diabetes.
• Best predictor: underlying maternal vascular disease.
• Highest risk groups:
• Retinal vasculopathy and/or renal vasculopathy
• Chronic hypertension

G) Other neonatal outcomes

• Infants of diabetic mothers:
• 5-fold higher rates of severe hypoglycaemia
• 2-fold increase in neonatal jaundice
• More birth injuries

H) Long-term child metabolic risk

• Excess fetal fat stores may extend into childhood/adult life.
• Children of diabetic pregnancies have more:
• Glucose intolerance
• Increased serum insulin
• By age 10–16 years:
• 19.3% rate of impaired glucose intolerance
• Childhood metabolic syndrome includes:
• Childhood obesity
• Hypertension
• Dyslipidaemia
• Glucose intolerance
• Greatest risk: infants born large for gestational age.
• Islet-cell–directed autoimmunity markers (if present) increase risk of type 1 diabetes.

9) Pre-Pregnancy Counselling for Women With Diabetes

A) Why it matters

• Major way to reduce diabetes-associated neonatal morbidity.

B) What must be assessed

• Cardiovascular status
• Renal status
• Ophthalmological status

C) Monitoring plan + targets

• Frequent monitoring of:
• Preprandial capillary glucose
• Postprandial capillary glucose
• Target plasma goals:
• Fasting plasma glucose: 5.0–5.5 mmol/L
• 1-hour postprandial: < 7.8 mmol/L
• 2-hour postprandial: < 6.7 mmol/L
• HbA1c:
• Ideally within reference range for at least 3 months before conception

D) Folic acid

• Vitamin supplement containing at least 1.0 mg/day folic acid
• For at least 3 months before conception
• Purpose: minimise neural tube defects

E) Other counselling components

• Review:
• Body weight
• Smoking
• Blood pressure control
• Oral medications such as ACE inhibitors and statins

10) Management of Diabetes During Pregnancy

A) Nutrition therapy (all women, including GDM)

• Nutritional counselling for GDM, as in all diabetes.
• Individualise medical nutrition therapy by maternal weight/height.

For obesity (BMI > 30 kg/m²):

• 30–33% calorie restriction (to 25 kcal/kg actual weight/day) reduces:
• Hyperglycaemia
• Plasma triglycerides
• with no increase in ketonuria

Carbohydrate proportion

• Restrict carbohydrates to 35–40% of calories:
• decreases maternal glucose
• improves maternal and fetal outcomes

Exercise

• Moderate physical exercise lowers maternal glucose in GDM.

B) Insulin therapy

• Most consistently reduces fetal morbidities when added to nutrition therapy.

Who gets insulin?

• Based on maternal glycaemia (with or without fetal growth assessment).
• Recommended when diet fails to maintain self-monitored whole-blood glucose below:
• 5.3 mmol/L fasting
• 7.8 mmol/L 1 hour postprandial
• 6.7 mmol/L 2 hours postprandial

Equivalent plasma glucose values

• 5.8 mmol/L, 8.6 mmol/L, 7.2 mmol/L respectively.

Goal

• Achieve glucose profiles similar to pregnant women without diabetes.

Insulins considered safe/efficacious

• Insulin lispro
• Insulin aspart
• Regular insulin
• Isophane insulin

Dose changes

• Regimens must be continuously modified from 1st to 3rd trimester as resistance rises.

Pump

• Subcutaneous continuous insulin infusion may improve control in select women.

C) Oral glucose-lowering agents

• Generally not recommended.

Metformin

• Biguanide; mainly decreases hepatic glucose output.
• Crosses placenta; cord levels higher than maternal.
• PCOS pregnancy studies with 1.5–2.5 g/day through pregnancy suggest relative safety in 2nd and 3rd trimesters.
• Use in type 2 diabetes in pregnancy to reduce insulin levels needs further investigation.

Glibenclamide

• Sulphonylurea; minimally transported across placenta.
• Studies suggest as safe and efficacious as insulin in type 2 diabetes.
• Success rate for glycaemic control ~80%
• Safe in breastfeeding with no transfer into human milk.

D) Antihypertensives/statins in diabetic women

• ACE inhibitors are contraindicated in 2nd and 3rd trimesters:
• interfere with fetal renal development
• cause oligohydramnios and fetal growth restriction
• Methyldopa is drug of choice
• Atenolol and nifedipine at therapeutic doses may be safe alternatives
• Statins contraindicated during pregnancy

11) Monitoring of Pregnant Women With Diabetes

A) Purpose

• Detect hyperglycaemia severe enough to increase fetal risk.

B) Maternal monitoring

• Self-monitor blood glucose every day.
• In insulin-treated diabetes:
• success depends on glycaemic targets set and achieved
• Frequency/timing of home monitoring should be individualised.
• Must monitor both:
• preprandial glucose
• postprandial glucose
• Urine glucose monitoring is not useful in GDM.
• Monitor:
• Blood pressure
• Urine protein to detect hypertensive disorders.

C) When to increase surveillance

• Particularly when:
• fasting glucose levels exceed 5.8 mmol/L, or
• pregnancy progresses past term.

D) Fetal monitoring

• Ultrasound assessment for fetal growth, especially early 3rd trimester:
• helps identify fetuses that may benefit from maternal insulin therapy.

12) Long-Term Therapeutic Considerations After GDM

A) Postpartum testing schedule

• Check maternal glycaemic status ≥ 6 weeks after delivery.
• If normal:
• reassess at least every 3 years
• If impaired fasting glucose or impaired glucose tolerance postpartum:
• test for diabetes annually
• provide intensive diet/lifestyle advice
• counsel on need for family planning
• Oral contraceptives can be used in women with prior GDM.
• Advise medical attention if symptoms suggest diabetes.

B) Child follow-up

• Children of women with GDM should be followed for:
• obesity
• abnormalities of glucose tolerance

13) NICE Guidance — Key Priorities (Preconception → Postnatal)

A) Pre-conception care

• Inform women good glycaemic control before conception and throughout pregnancy reduces risk of:
• miscarriage
• congenital malformation
• stillbirth
• neonatal death (risks reduced, not eliminated)
• Avoid unplanned pregnancy: essential component of diabetes education from adolescence.
• Offer pre-conception care/advice before discontinuing contraception.

B) Antenatal care

• Aim targets (if safely achievable):
• fasting blood glucose 3.5–5.9 mmol/L
• 1-hour postprandial < 7.8 mmol/L
• Insulin-treated diabetes:
• advise about hypoglycaemia and hypoglycaemia unawareness, especially 1st trimester
• Suspected diabetic ketoacidosis:
• immediate admission for critical care with medical + obstetric care
• Offer fetal cardiac assessment:
• four-chamber view and outflow tracts at 18–20 weeks

C) Neonatal care

• Babies should be kept with mothers unless:
• clinical complication, or
• abnormal clinical signs needing intensive/special care admission

D) Postnatal care (after GDM)

• Offer lifestyle advice:
• weight control, diet, exercise
• Offer fasting plasma glucose (not OGTT) at:
• 6-week postnatal check
• annually thereafter

E) Advice & information topics (explicit list)

• risks of diabetes in pregnancy + reduction with good control
• diet, body weight, exercise, including weight loss if BMI > 27 kg/m²
• hypoglycaemia and hypoglycaemia unawareness
• pregnancy-related nausea/vomiting and glycaemic control
• retinal and renal assessment
• when to stop contraception
• folic acid 5 mg/day from pre-conception until 12 weeks
• review of medication, glycaemic targets, self-monitoring routine
• frequency of appointments + local support + emergency telephone numbers

14) NICE — Gestational Diabetes: Risk Factors + Screening Rules

A) Risk factors for screening

• BMI above 30 kg/m²
• Previous macrosomic baby ≥ 4.5 kg
• Previous gestational diabetes
• First-degree relative with diabetes
• Family origin with high prevalence of diabetes:
• South Asian
• black Caribbean
• Middle Eastern

B) Screening and diagnosis — Offer

• Risk-factor screening at booking appointment
• If previous GDM:
• early self-monitoring of blood glucose or 2-hour 75 g OGTT at 16–18 weeks
• if normal → OGTT at 28 weeks
• If any other risk factor:
• OGTT at 24–28 weeks

C) Do not offer (NICE)

• Do not offer screening using:
• fasting plasma glucose
• random blood glucose
• glucose challenge test
• urinalysis for glucose

D) Information before screening/testing

• Small risk of birth complications if GDM not controlled
• Most respond to diet and exercise
• Oral hypoglycaemics or insulin may be needed if not controlled
• Extra monitoring/care may be needed during pregnancy and labour

15) Obesity and Pregnancy

A) Fertility and IVF effects

• Obesity associated with:
• reduced fertility
• negative effects on IVF outcomes

B) Endocrine state and menstrual effects

• Hyperinsulinaemic + hyperandrogenaemic state → may cause:
• oligo/amenorrhoea
• often with polycystic ovarian syndrome

C) Infertility risk

• Relative risk of anovulatory infertility up to 3:1 when BMI > 27 kg/m²

D) Pregnancy risks increased in obese women

• Increased risk of:
• stillbirth or intrauterine fetal death
• preterm labour
• miscarriage
• fetal chromosomal anomalies
• macrosomia
• Greater incidence of:
• dysfunctional labour
• caesarean section + perioperative morbidity
• postpartum haemorrhage
• More likely to suffer from:
• thromboembolism
• gestational diabetes
• pregnancy-induced hypertension
• pre-eclampsia
• proteinuria after 20 weeks of pregnancy