ADRENAL GLAND — STRUCTURE, HORMONES & FUNCTION (LOGIC-BASED MASTER NOTE)

I. BIG PICTURE OVERVIEW

1️⃣ Two endocrine organs in one gland

The adrenal gland contains two embryologically, structurally, and functionally distinct endocrine organs:

II. ADRENAL MEDULLA — LOGIC

2️⃣ Functional identity

• The adrenal medulla is essentially a modified sympathetic ganglion
• Key modification:
• Postganglionic neurons have lost their axons
• They have become secretory cells
• Innervation:
• Preganglionic sympathetic fibers
• Travel via splanchnic nerves
• Release acetylcholine (ACh)

👉 Therefore:

Neural stimulus → hormonal release into blood

3️⃣ Hormones secreted

• Epinephrine (major in humans & dogs)
• Norepinephrine
• Small amounts of dopamine

📌 Purpose:

Prepare the body for emergency responses (fight-or-flight)

III. ADRENAL CORTEX — LOGIC

4️⃣ Hormone classes

📌 Glucocorticoids + mineralocorticoids are essential for survival

5️⃣ Control of secretion

• ACTH (anterior pituitary):
• Primary control of glucocorticoids
• Trophic to zona fasciculata & reticularis
• Angiotensin II:
• Primary regulator of aldosterone
• Acts independently of ACTH

IV. ADRENAL MORPHOLOGY — MEDULLA

6️⃣ Structural features

• Forms 28% of adrenal mass
• Cells arranged as:
• Interlacing cords
• Closely apposed to venous sinusoids
• Densely innervated

7️⃣ Medullary cell types

❓ Dopamine-secreting cell morphology → unknown

8️⃣ Paraganglia

• Extra-adrenal collections of medullary-like cells
• Located near:
• Thoracic sympathetic ganglia
• Abdominal sympathetic ganglia

V. ADRENAL MORPHOLOGY — CORTEX

9️⃣ Cortical zones (adult)

📌 Cells contain abundant lipid, especially in zona fasciculata.

🔬 Enzymatic specialization

• All zones → secrete corticosterone
• Aldosterone enzymes → only zona glomerulosa
• Cortisol + sex hormone enzymes → inner two zones
• Functional dominance:
• Fasciculata → glucocorticoids
• Reticularis → androgens

VI. ADRENAL BLOOD SUPPLY — EXAM FAVORITE

🔁 Dual supply

• Arterial input:
• Phrenic arteries
• Renal arteries
• Aorta
• Blood flow:
• Capsule plexus → cortex → medullary sinusoids
• PLUS direct arterioles to medulla
• Venous drainage:
• Single central adrenal vein
• Flow is very high (typical endocrine gland feature)

📌 Functional consequence:

Cortical hormones bathe the medulla

VII. FETAL ADRENAL — UNIQUE HUMAN FEATURE

🔹 Structure

• In fetus:
• Adrenal is large
• 80% = fetal cortex
• 20% = permanent cortex
• Fetal cortex:
• Degenerates rapidly after birth

🔹 Function

• Produces sulfated androgens
• Placenta converts them → estrogens

📌 No comparable structure in lab animals

VIII. CORTICAL CELL RENEWAL & PITUITARY EFFECTS

🔁 Regeneration

• Zona glomerulosa:
• Source of new cortical cells
• Removal of fasciculata & reticularis:
• These regenerate from glomerular cells

🚫 Medulla does NOT regenerate

🧠 Hypophysectomy effects

• Aldosterone initially normal
• Long-term hypopituitarism → aldosterone deficiency
• ACTH:
• Hypertrophies inner zones
• Shrinks zona glomerulosa

IX. STEROID-SECRETING CELL ULTRASTRUCTURE

• Smooth endoplasmic reticulum → steroid synthesis
• Mitochondria → key enzymatic steps
• Same structure across all steroid-secreting tissues

🧠 ADRENAL GLAND — COMPLETE LOGIC-BASED MASTER TABLE (ZERO OMISSION)

✅ EXAM LOCK (one-line logic summary)

Medulla = neural stress hormones; Cortex = layered steroid factory; Glomerulosa survives without ACTH; Fasciculata & Reticularis die without ACTH; Fetal cortex feeds placenta.

ADRENAL MEDULLA — HORMONES & MECHANISMS

X. CATECHOLAMINES

🔹 Species differences

📌 Norepinephrine also enters blood from sympathetic nerve endings

🔹 Biosynthesis logic

• Tyrosine → DOPA → Dopamine → Norepinephrine → Epinephrine
• PNMT:
• Converts NE → E
• Present mainly in brain & adrenal medulla
• Induced by glucocorticoids

👉 Cortisol-rich blood from cortex → stimulates epinephrine synthesis

🔹 Developmental link

• 21β-hydroxylase deficiency:
• ↓ fetal glucocorticoids
• → medullary dysplasia
• → ↓ catecholamines after birth

XI. PLASMA HANDLING & METABOLISM

🔹 Conjugation

• Sulfate conjugates = inactive

🔹 Normal plasma levels

• Standing → NE ↑ 50–100%
• Adrenalectomy:
• NE unchanged
• E → zero (later low reappearance from unknown source)

🔹 Metabolism

• Half-life ≈ 2 min
• Metabolized to:
• Metanephrine / normetanephrine
• VMA

Daily urinary excretion:

• NE ≈ 30 μg
• E ≈ 6 μg
• VMA ≈ 700 μg

XII. MEDULLARY CO-SECRETED SUBSTANCES

• Stored with:
• ATP
• Chromogranin A
• Secretion mechanism:
• ACh → Ca²⁺ influx → exocytosis
• Also secreted:
• Met-enkephalin (opioid peptide)
• Adrenomedullin (vasodepressor)

📌 Opioids do not cross BBB

XIII. EFFECTS OF EPINEPHRINE & NOREPINEPHRINE

🔹 Receptor classes

• α₁, α₂
• β₁, β₂, β₃

❤️ Cardiovascular

🧠 CNS

• ↑ Alertness
• Epinephrine → more anxiety & fear

🍬 Metabolic

• Glycogenolysis (liver & muscle)
• ↑ FFA
• ↑ Lactate
• ↑ Metabolic rate (biphasic)
• Cold intolerance in catecholamine-deficient mice

🧂 Potassium

• Initial ↑ plasma K⁺
• Sustained ↓ plasma K⁺ (β₂-mediated muscle uptake)

🧪 Threshold plasma levels (epinephrine)

📌 NE rarely reaches systemic threshold → acts mainly locally

🩺 Pheochromocytoma

• Sustained hypertension
• 15% epinephrine-secreting tumors:
• Episodic palpitations
• Headache
• Glycosuria
• Extreme systolic HTN

XIV. EFFECTS OF DOPAMINE

• Physiologic role in circulation → unclear
• Actions:
• Renal vasodilation (dopaminergic receptors)
• Mesenteric vasodilation
• Cardiac inotropy (β₁)
• ↑ SBP, unchanged DBP
• Renal dopamine:
• Causes natriuresis
• Inhibits Na⁺/K⁺-ATPase
• Clinical use:
• Traumatic & cardiogenic shock

🧠 ADRENAL MEDULLA — CATECHOLAMINES (MASTER TABLE SET)

1️⃣ Species Differences in Catecholamine Secretion

Exam note:

📌 Norepinephrine also enters circulation from sympathetic nerve endings (not only adrenal medulla).

2️⃣ Biosynthesis of Catecholamines (Logic Table)

PNMT (Phenylethanolamine-N-methyltransferase)

3️⃣ Developmental Link — 21β-Hydroxylase Deficiency

4️⃣ Plasma Handling — Conjugation

📌 Sulfate-conjugated catecholamines are biologically inactive.

5️⃣ Normal Plasma Levels

Physiologic Modifiers

6️⃣ Metabolism & Excretion

Daily Urinary Excretion

7️⃣ Medullary Co-Secreted Substances

Stored Together With Catecholamines

Secretion Mechanism

Other Secreted Substances

📌 Opioid peptides do NOT cross the blood–brain barrier.

8️⃣ Adrenergic Receptors

Receptor Classes

α₁, α₂

β₁, β₂, β₃

9️⃣ Cardiovascular Effects

🔟 CNS Effects

1️⃣1️⃣ Metabolic Effects

1️⃣2️⃣ Potassium Effects

1️⃣3️⃣ Threshold Plasma Levels — Epinephrine

📌 NE rarely reaches systemic threshold → acts mainly locally.

1️⃣4️⃣ Pheochromocytoma

1️⃣5️⃣ Dopamine — Effects & Clinical Use

Renal Dopamine Actions

Clinical Use

Indication

Traumatic shock

Cardiogenic shock

ADRENAL GLAND — REGULATION, STRUCTURE, BIOSYNTHESIS & ENZYME DEFECTS (LOGIC NOTE)

PART A — ADRENAL MEDULLA

Regulation of Adrenal Medullary Secretion

1️⃣ Core Principle

• Adrenal medulla = modified sympathetic ganglion
• Secretion is neural, not hormonal
• Physiologic stimuli → CNS → sympathetic outflow → adrenal medulla

2️⃣ Basal Secretion

• Catecholamine secretion is low at rest
• During sleep:
• Epinephrine ↓
• Norepinephrine ↓ further

👉 Confirms tonic sympathetic dependence

3️⃣ Emergency / Stress Response

• Part of diffuse sympathetic discharge
• Described by Cannon as:

“Emergency function of the sympathoadrenal system”

Situations:

• Fear
• Trauma
• Exercise
• Hypoglycemia
• Cold exposure

4️⃣ Functional Importance of Circulating Catecholamines

Especially important when systemic metabolic support is needed:

A. Cold exposure

• Catecholamines → calorigenic effect
• ↑ heat production

B. Hypoglycemia

• Catecholamines → glycogenolysis
• ↑ blood glucose

5️⃣ Selective Secretion (HIGH-YIELD EXAM LOGIC)

🔑 Total secretion ↑, but NE:E ratio usually unchanged

PART B — ADRENAL CORTEX

Structure & Classification of Adrenocortical Hormones

6️⃣ Steroid Core Structure

• All adrenal cortical hormones are cholesterol derivatives
• Share cyclopentanoperhydrophenanthrene nucleus

Same family as:

• Gonadal steroids
• Bile acids
• Vitamin D

7️⃣ Steroid Carbon Classification

8️⃣ Functional Classification (Selye)

C21 Steroids

• Mineralocorticoids
• Na⁺ retention
• K⁺ excretion
• Glucocorticoids
• Glucose metabolism
• Protein catabolism

⚠️ All C21 steroids have BOTH activities

→ classification depends on predominant effect

9️⃣ Steroid Configuration Rules (Exam Traps)

• Δ → double bond
• β (solid line) → above plane
• α (dashed) → below plane

Naturally occurring adrenal steroids:

• Δ⁴-3-keto A-ring
• 17-OH → α configuration
• 3, 11, 21-OH → β configuration
• Aldosterone → 18-aldehyde (D-form)
• L-aldosterone = inactive

🔟 Steroids Secreted in Physiologic Amounts

Mineralocorticoid

• Aldosterone

Glucocorticoids

• Cortisol
• Corticosterone

Androgens

• DHEA
• Androstenedione

1️⃣1️⃣ Special Steroid Notes

• Deoxycorticosterone (DOC)
• Secreted ≈ aldosterone
• Only 3% mineralocorticoid potency
• Clinically relevant only when ↑
• Adrenal estrogens
• Derived peripherally from androstenedione
• DHEA
• Secreted mainly as DHEA-S
• Others secreted unconjugated

1️⃣2️⃣ Species Differences (Exam Favorite)

PART C — STEROID BIOSYNTHESIS

Pathway Logic

1️⃣3️⃣ Cholesterol Handling

• Source:
• Mostly from LDL uptake
• LDL receptors abundant in adrenal cortex
• Stored as cholesterol esters in lipid droplets
• Cholesterol ester hydrolase → free cholesterol

1️⃣4️⃣ Rate-Limiting Step

• Transport into mitochondria via StAR protein
• Conversion to pregnenolone
• Enzyme:
• Cholesterol desmolase
• P450scc
• CYP11A1
• Location: Mitochondria

1️⃣5️⃣ Smooth ER Reactions

3β-Hydroxysteroid Dehydrogenase

(Not a P450)

Converts:

• Pregnenolone → Progesterone
• 17-OH pregnenolone → 17-OH progesterone
• DHEA → Androstenedione

1️⃣6️⃣ 17α-Hydroxylase / 17,20-Lyase

• CYP17
• Produces:
• 17-OH steroids
• C19 androgens

1️⃣7️⃣ 21β-Hydroxylase

• CYP21A2
• SER enzyme
• Forms:
• 11-deoxycorticosterone
• 11-deoxycortisol

1️⃣8️⃣ Final Mitochondrial Step

11β-Hydroxylase

• CYP11B1
• Converts:
• DOC → Corticosterone
• 11-deoxycortisol → Cortisol

1️⃣9️⃣ Aldosterone Synthase

• CYP11B2
• Present only in zona glomerulosa
• Absent:
• 17α-hydroxylase
• 11β-hydroxylase

👉 Explains aldosterone only

2️⃣0️⃣ Zonal Specialization

PART D — REGULATION

ACTH & ANGIOTENSIN II

2️⃣1️⃣ ACTH

• Receptor → Gs
• ↑ adenylyl cyclase → ↑ cAMP
• Immediate: ↑ pregnenolone
• Chronic: ↑ P450 enzyme synthesis

2️⃣2️⃣ Angiotensin II

• Acts on AT1 receptors
• Via PLC → PKC
• Selectively ↑ aldosterone

PART E — ENZYME DEFICIENCIES (CONGENITAL ADRENAL HYPERPLASIA)

2️⃣3️⃣ General Rule

• ↓ Cortisol → ↑ ACTH → adrenal hyperplasia

2️⃣4️⃣ Key Defects

A. Cholesterol desmolase deficiency

• Fatal in utero
• Placenta can’t make progesterone

B. StAR deficiency

• Congenital lipoid adrenal hyperplasia
• ↓ all steroids
• Female external genitalia regardless of genotype

C. 3β-HSD deficiency

• ↑ DHEA
• Mild virilization in females
• Hypospadias in males

D. 17α-Hydroxylase deficiency

• ↓ Sex steroids
• ↑ DOC → hypertension + hypokalemia
• Corticosterone partially compensates cortisol

E. 21β-Hydroxylase deficiency (MOST COMMON – 90%)

• ↓ Cortisol ± aldosterone
• ↑ Androgens → virilization
• 75% = salt-losing

F. 11β-Hydroxylase deficiency

• ↑ DOC → hypertension
• Virilization present

2️⃣5️⃣ Treatment Principle

• Glucocorticoids
• Replace cortisol
• Suppress ACTH
• ↓ androgen excess

2️⃣6️⃣ Transcriptional Control

• Enzyme expression depends on Steroid Factor-1 (SF-1)
• Knockout → no adrenal + gonadal development

PART F — SYNTHETIC STEROIDS (CLINICAL BOX LOGIC)

• Structural modification → ↑ potency
• Dexamethasone
• High receptor affinity
• Long half-life
• Strong glucocorticoid, minimal mineralocorticoid

FINAL EXAM LOCK

• Medulla = neural
• Cortex = steroid + zonal enzyme logic
• ACTH → cortisol
• Ang II → aldosterone
• ↓ cortisol = ↑ ACTH = hyperplasia
• 21β-hydroxylase = most common defect

🧠 ADRENAL GLAND — COMPLETE MASTER TABLES (EXAM-READY)

TABLE 1 — ADRENAL MEDULLA: REGULATION & PHYSIOLOGY

TABLE 2 — BASAL vs STRESS SECRETION (MEDULLA)

TABLE 3 — STRESS TYPES & CATECHOLAMINE DOMINANCE (EXAM FAVORITE)

TABLE 4 — PHYSIOLOGIC IMPORTANCE OF CIRCULATING CATECHOLAMINES

🧱 ADRENAL CORTEX

TABLE 5 — STEROID CORE STRUCTURE

TABLE 6 — STEROID CARBON CLASSIFICATION

TABLE 7 — FUNCTIONAL CLASSIFICATION (SELYE)

TABLE 8 — STEROID CONFIGURATION RULES (EXAM TRAPS)

TABLE 9 — PHYSIOLOGICALLY SECRETED ADRENAL STEROIDS

TABLE 10 — SPECIAL STEROID NOTES

TABLE 11 — SPECIES DIFFERENCES (HIGH-YIELD)

⚙️ STEROID BIOSYNTHESIS

TABLE 12 — CHOLESTEROL HANDLING

TABLE 13 — RATE-LIMITING STEP

TABLE 14 — SMOOTH ER ENZYMES

TABLE 15 — KEY BIOSYNTHETIC ENZYMES

TABLE 16 — ZONAL SPECIALIZATION

🎯 REGULATION

TABLE 17 — ACTH vs ANGIOTENSIN II

🧬 CONGENITAL ADRENAL HYPERPLASIA (CAH)

TABLE 18 — GENERAL RULE

Core Logic

↓ Cortisol → ↑ ACTH →

Adrenal hyperplasia

TABLE 19 — ENZYME DEFECTS (ZERO-OMISSION)

TABLE 20 — TREATMENT PRINCIPLE

TABLE 21 — TRANSCRIPTIONAL CONTROL

💊 SYNTHETIC STEROIDS

TABLE 22 — DEXAMETHASONE (CLINICAL LOGIC)

🔐 FINAL EXAM LOCK TABLE

TRANSPORT, METABOLISM & EXCRETION OF ADRENOCORTICAL HORMONES

(Logic-Based Core Note — Zero Omission)

I. TRANSPORT IN BLOOD: WHY BINDING MATTERS

1️⃣ Glucocorticoid binding proteins

• Cortisol circulates mainly bound to:
• CBG (corticosteroid-binding globulin)
• Also called transcortin
• An α-globulin
• Albumin → minor contribution
• Corticosterone:
• Binds similarly but less tightly than cortisol

2️⃣ Functional consequences of binding

• Protein-bound steroid = physiologically inactive
• Only free hormone:
• Enters tissues
• Produces biological effects
• Regulates ACTH feedback
• Because most cortisol is bound:
• Very little free cortisol or corticosterone appears in urine

3️⃣ Half-life differences explained by binding

• Cortisol
• Stronger binding → longer half-life
• ≈ 60–90 minutes
• Corticosterone
• Weaker binding → shorter half-life
• ≈ 50 minutes

4️⃣ CBG as a circulating hormone reservoir (KEY CONCEPT)

• Bound cortisol acts as a buffered storage pool
• Maintains a steady free cortisol supply to tissues
• Analogy:
• Same principle as T4 bound to thyroxine-binding proteins
• Prevents rapid fluctuations in hormone action

5️⃣ Saturation of CBG: when free cortisol rises sharply

• Normal total plasma cortisol
• ≈ 13.5 μg/dL (375 nmol/L)
• → Very little is free
• CBG saturation point
• ≈ 20 μg/dL
• Beyond this:
• CBG binding sites are full
• Albumin binding increases slightly
• Major increase occurs in free cortisol fraction

6️⃣ Regulation of CBG synthesis

• Synthesized in the liver
• Estrogen increases CBG production

Clinical states affecting CBG:

7️⃣ ACTH feedback adaptation to CBG changes

When CBG increases (eg pregnancy):

1. More cortisol becomes bound
2. Free cortisol initially falls
3. ↓ Free cortisol → ↑ ACTH
4. ACTH stimulates more cortisol secretion
5. New steady state:
• High total cortisol
• Normal free cortisol
• No Cushingoid features

When CBG decreases (eg nephrosis):

1. Less cortisol binding
2. Total cortisol falls
3. Free cortisol remains normal
4. No adrenal insufficiency symptoms

📌 Explains key clinical paradox:

• Pregnancy → high total cortisol, no excess
• Nephrosis → low total cortisol, no deficiency

II. METABOLISM & EXCRETION OF GLUCOCORTICOIDS

1️⃣ Primary site of metabolism

• Liver = main site of glucocorticoid catabolism

2️⃣ Major metabolic pathway of cortisol

1. Cortisol
2. → Dihydrocortisol
3. → Tetrahydrocortisol
4. → Glucuronide conjugation
• Via glucuronyl transferase
5. → Water-soluble metabolite

3️⃣ Glucuronyl transferase system — broader role

• Same enzyme system conjugates:
• Bilirubin
• Other steroid hormones
• Many drugs
• Competitive inhibition occurs among substrates
• High levels of one can slow metabolism of others

4️⃣ 11β-Hydroxysteroid dehydrogenase (11β-HSD)

Two isoenzymes with distinct roles:

🔹 Type 1 (11β-HSD1)

• Bidirectional enzyme
• Converts:
• Cortisol ⇄ cortisone
• Predominant action:
• Reductase
• Generates active cortisol

🔹 Type 2 (11β-HSD2)

• Unidirectional
• Converts:
• Cortisol → cortisone
• Protects mineralocorticoid receptors from cortisol

5️⃣ Cortisone — key clarifications

• Active glucocorticoid (after conversion to cortisol)
• Widely used therapeutically
• Not secreted significantly by adrenal cortex
• Cortisone formed in liver:
• Is rapidly reduced
• Conjugated to tetrahydrocortisone glucuronide
• Does not re-enter circulation in free form

6️⃣ Final excretion of glucocorticoids

• Tetrahydro-glucuronide conjugates:
• Freely water soluble
• Do NOT bind plasma proteins
• Rapidly excreted in urine

7️⃣ Minor metabolic pathways

• ≈ 10% of cortisol
• Converted to 17-ketosteroids
• Via side-chain cleavage in liver
• These are:
• Mostly sulfate-conjugated
• Excreted in urine
• Additional metabolites:
• 20-hydroxy derivatives
• Enterohepatic circulation present
• ≈ 15% of secreted cortisol
• Excreted in stool

8️⃣ Corticosterone metabolism

• Follows same pathways as cortisol
• Key exception:
• Does NOT form 17-ketosteroid derivatives

III. ALDOSTERONE: DISTINCT HANDLING

1️⃣ Transport characteristics

• Minimal protein binding
• Short half-life ≈ 20 minutes

2️⃣ Plasma concentration (comparison)

• Aldosterone:
• ≈ 0.006 μg/dL (0.17 nmol/L)
• Cortisol:
• ≈ 13.5 μg/dL (375 nmol/L)
• Aldosterone secretion is much smaller

3️⃣ Metabolism of aldosterone

• Liver converts much of it to:
• Tetrahydroglucuronide
• Liver + kidney also form:
• 18-glucuronide

4️⃣ Acid-labile conjugate (HIGH-YIELD)

• 18-glucuronide:
• Hydrolyzed to free aldosterone at pH 1.0
• Therefore called acid-labile conjugate
• Unique among steroid metabolites

5️⃣ Urinary excretion pattern

IV. 17-KETOSTEROIDS

1️⃣ Sources

• Major adrenal androgen:
• Dehydroepiandrosterone (DHEA)
• Also secreted:
• Androstenedione
• Additional contributors:
• Cortisol & cortisone metabolites
• Testosterone metabolism

2️⃣ 11-oxy-17-ketosteroids

• Only steroids with 11-OH or =O at C-11:
• 11-hydroxy-androstenedione
• Cortisol & cortisone metabolites
• Formed in liver via side-chain cleavage

3️⃣ Daily urinary excretion

• Men: ≈ 15 mg/day
• Women: ≈ 10 mg/day

Origin in men:

• ≈ ⅔ adrenal-derived
• ≈ ⅓ testicular

4️⃣ Etiocholanolone — clinical relevance

• Metabolite of:
• Adrenal androgens
• Testosterone
• When unconjugated:
• Causes fever
• Some individuals develop:
• Etiocholanolone fever
• Due to episodic accumulation in blood

V. VARIATIONS IN HEPATIC METABOLISM (CLINICAL BOX)

• Hepatic inactivation of glucocorticoids is reduced in:
• Liver disease
• Surgery
• Stress
• Result:
• Free cortisol rises higher
• Even more than with maximal ACTH alone
• Explains exaggerated cortisol responses during stress

🟩 TABLE 1 — TRANSPORT OF ADRENOCORTICAL HORMONES (CORE LOGIC)

🟩 TABLE 2 — CBG (TRANSCORTIN): PROPERTIES & REGULATION

🟩 TABLE 3 — CBG SATURATION & PLASMA CORTISOL DYNAMICS

🟩 TABLE 4 — CLINICAL STATES AFFECTING CBG

🟩 TABLE 5 — ACTH FEEDBACK ADAPTATION (EXAM PARADOX)

🟩 TABLE 6 — GLUCOCORTICOID METABOLISM: MAJOR PATHWAY

🟩 TABLE 7 — GLUCURONYL TRANSFERASE: SYSTEMIC ROLE

🟩 TABLE 8 — 11β-HYDROXYSTEROID DEHYDROGENASE (11β-HSD)

🟩 TABLE 9 — CORTISONE: EXAM CLARIFICATIONS

🟩 TABLE 10 — MINOR METABOLIC PATHWAYS OF CORTISOL

🟩 TABLE 11 — CORTICOSTERONE METABOLISM

🟩 TABLE 12 — ALDOSTERONE: TRANSPORT & METABOLISM (HIGH-YIELD)

🟩 TABLE 13 — ACID-LABILE CONJUGATE (EXAM GOLD)

🟩 TABLE 14 — URINARY EXCRETION OF ALDOSTERONE

🟩 TABLE 15 — 17-KETOSTEROIDS: SOURCES & EXCRETION

🟩 TABLE 16 — 11-OXY-17-KETOSTEROIDS

🟩 TABLE 17 — ETIOCHOLANOLONE (CLINICAL PEARL)

🟩 TABLE 18 — VARIATIONS IN HEPATIC METABOLISM (CLINICAL BOX)

EFFECTS OF ADRENAL ANDROGENS, ESTROGENS & GLUCOCORTICOIDS

(Logic-Based | Zero Omission | Re-audited)

I. ADRENAL ANDROGENS — CORE LOGIC

1. What adrenal androgens are

• Androgens = hormones with masculinizing effects
• Also promote protein anabolism and growth
• Testosterone (from testes) = most potent androgen
• Adrenal androgens:
• Have < 20% of testosterone’s androgenic activity

2. Control of adrenal androgen secretion

• Acute control:
• Regulated by ACTH
• NOT regulated by gonadotropins (LH/FSH)
• Long-term pattern (DHEAS):
• Plasma DHEAS rises gradually
• Peaks in early 20s (~225 μg/dL)
• Declines progressively to very low levels in old age
• Important insight:
• These long-term changes are NOT due to ACTH
• Caused by:
• Increase → then gradual decrease in 17α-hydroxylase lyase activity

3. Circulating form

• DHEA is mostly inactive unless converted
• ~99.7% of DHEA is sulfated
• Circulates as DHEAS
• Only ~0.3% is free DHEA

4. Physiologic androgenic impact

• Adrenal androgen secretion:
• Nearly equal in:
• Castrated males
• Females
• Normal males
• Therefore:
• Minimal masculinization at normal levels

5. Effects of excess adrenal androgens

• Adult males:
• Only accentuate existing male traits
• Prepubertal boys:
• Cause precocious pseudopuberty
• Secondary sex characteristics develop
• NO testicular enlargement
• Females:
• Cause:
• Female pseudohermaphroditism
• Adrenogenital syndrome

6. DHEA supplementation

• DHEA injections promoted by some for “anti-aging”
• Evidence:
• Results controversial
• No consistent proven benefit

II. ADRENAL ESTROGENS — LOGIC

1. Source

• Adrenal androstenedione:
• Converted in peripheral tissues (fat, others) to:
• Testosterone
• Estrogens (via aromatization)

2. Clinical importance

• Major estrogen source in:
• Men
• Postmenopausal women

III. ADRENAL INSUFFICIENCY — PHYSIOLOGIC FAILURE

1. Consequences without treatment

• Mineralocorticoid deficiency:
• Na⁺ loss
• Hypovolemia
• Shock
• Glucocorticoid deficiency:
• Abnormal metabolism of:
• Water
• Carbohydrates
• Proteins
• Fats
• Result:
• Fatal, even if mineralocorticoids alone are given

2. Role of glucocorticoids

• Small amounts:
• Correct metabolic abnormalities
• Act:
• Directly
• Permissively (allow other hormones to work)

IV. MECHANISM OF ACTION — GLUCOCORTICOIDS

1. Genomic actions

• Bind to glucocorticoid receptors
• Steroid-receptor complex:
• Acts as a transcription factor
• Alters gene transcription
• Leads to enzyme synthesis → altered cell function

2. Nongenomic actions

• Evidence suggests rapid, non-DNA mediated effects also exist

V. EFFECTS ON INTERMEDIARY METABOLISM

1. Carbohydrate metabolism

• ↑ Hepatic:
• Glycogenesis
• Gluconeogenesis
• ↑ Glucose-6-phosphatase
• ↑ Plasma glucose
• Peripheral anti-insulin effect

2. Protein metabolism

• ↑ Protein catabolism
• Amino acids → gluconeogenesis

3. Fat metabolism

• In diabetics:
• ↑ Lipolysis
• ↑ Ketone bodies
• In normal individuals:
• Insulin rise masks these effects

4. Organ protection

• Brain & heart:
• Spared from insulin antagonism
• Elevated glucose:
• Ensures supply to vital organs

5. Adrenal insufficiency & fasting

• Fed state:
• Plasma glucose normal
• Fasting:
• Severe hypoglycemia
• Can be fatal
• Adrenal cortex:
• Not essential for ketosis during fasting

VI. PERMISSIVE ACTION — KEY CONCEPT

Definition

• Glucocorticoids do not cause reactions
• But must be present for other hormones to act

Examples

• Required for:
• Glucagon & catecholamine calorigenic effects
• Catecholamine-induced lipolysis
• Catecholamine pressor responses
• Catecholamine bronchodilation

VII. EFFECT ON ACTH SECRETION

• Glucocorticoids:
• Inhibit ACTH secretion (negative feedback)
• Adrenalectomy:
• ↑ ACTH secretion

VIII. VASCULAR REACTIVITY

In adrenal insufficiency

• Vascular smooth muscle:
• Unresponsive to NE & epinephrine
• Capillary dilation
• ↑ Capillary permeability
• Failure of vascular compensation → collapse

Role of glucocorticoids

• Restore responsiveness to catecholamines
• Maintain vascular tone

IX. EFFECTS ON NERVOUS SYSTEM

In adrenal insufficiency

• EEG:
• Slower than normal β rhythm
• Personality changes:
• Irritability
• Apprehension
• Poor concentration
• Reversed only by glucocorticoids

X. WATER METABOLISM

Defect in adrenal insufficiency

• Cannot excrete water load
• Risk of water intoxication

Glucose fever

• Glucose infusion → fever → collapse → death
• Mechanism:
• Water dilutes plasma
• Hypothalamic cell swelling
• Thermoregulatory failure

Mechanisms involved

• ↑ Plasma vasopressin
• ↓ GFR
• Mineralocorticoids:
• Improve volume
• Glucocorticoids:
• Raise GFR more effectively

XI. BLOOD CELLS & LYMPHATIC ORGANS

Effects on circulating cells

• ↓ Eosinophils (sequestration)
• ↓ Basophils
• ↑ Neutrophils
• ↑ Platelets
• ↑ RBCs

Effects on lymphoid tissue

• ↓ Lymphocyte count
• ↓ Lymph node & thymus size
• Mechanism:
• ↓ Mitotic activity
• ↓ IL-2 (via NF-κB inhibition)
• ↑ Lymphocyte apoptosis

XII. RESISTANCE TO STRESS

Definition of stress

• Any threat to homeostasis

ACTH & survival

• Severe stress → ↑ ACTH → ↑ glucocorticoids
• Hypophysectomy or adrenalectomy:
• Animals die under stress

Why glucocorticoids are essential (partially understood)

• Maintain vascular reactivity
• Enable catecholamine-induced FFA mobilization
• Prevent excessive stress responses

Long-term excess

• Chronic ACTH elevation:
• Harmful
• Leads to Cushing syndrome

XIII. CUSHING SYNDROME — PATHOLOGIC EXCESS

1. Definition

• Clinical state of chronic glucocorticoid excess

2. ACTH-independent causes

• Adrenal tumors
• Adrenal hyperplasia
• Prolonged exogenous steroids
• Abnormal receptor expression:
• GIP
• Vasopressin
• β-adrenergic agonists
• IL-1
• GnRH

3. ACTH-dependent causes

• Pituitary adenomas (Cushing disease)
• Ectopic ACTH secretion (lung tumors)
• CRH-secreting tumors

4. Protein catabolism effects

• Thin skin
• Muscle wasting
• Poor wound healing
• Easy bruising
• Thin hair
• Acne & facial hair (from adrenal androgens)

5. Fat redistribution

• Thin limbs
• Central obesity
• Moon face
• Buffalo hump
• Purple striae (dermal rupture)

6. Metabolic effects

• Hyperglycemia
• Insulin-resistant diabetes
• Hyperlipidemia
• Ketosis (usually no severe acidosis)

7. Mineralocorticoid effects

• Salt & water retention
• K⁺ loss
• Weakness
• Hypertension (~85%)

8. Bone effects

• ↓ Bone formation
• ↑ Bone resorption
• Osteoporosis
• Vertebral collapse

9. CNS effects

• EEG acceleration
• Mood changes → psychosis possible

XIV. ANTI-INFLAMMATORY & ANTI-ALLERGIC ACTIONS

Mechanisms

• NF-κB inhibition
• ↓ Cytokine production
• Inhibition of phospholipase A₂
• ↓ Prostaglandins, leukotrienes, thromboxanes

Clinical danger

• Mask infection symptoms
• Without antibiotics → infection spreads
• Sudden steroid withdrawal:
• Severe adrenal insufficiency

XV. OTHER EFFECTS

• ↓ Growth & GH secretion
• ↓ TSH secretion
• ↑ PNMT
• Fetal lung surfactant maturation

XVI. REGULATION OF GLUCOCORTICOID SECRETION

Role of ACTH

• Essential for:
• Basal secretion
• Stress-induced secretion
• Angiotensin II:
• Minor effect (aldosterone)

ACTH chemistry

• 39-aa polypeptide
• Derived from POMC
• First 23 aa = active core
• Half-life ≈ 10 min

Effect on adrenal

• Output ↑ within minutes
• Dose-response:
• Log-linear at low doses
• Ceiling effect at max output

Adrenal responsiveness

• Chronic ACTH:
• ↑ sensitivity
• ACTH suppression:
• ↓ responsiveness
• Detectable within 24 h

Circadian rhythm

• ACTH bursts
• 75% cortisol between 4–10 AM
• Controlled by suprachiasmatic nucleus

Stress response

• Severe stress → ACTH exceeds max needed
• CRH from hypothalamus is main driver

Feedback

• Free cortisol:
• Inhibits ACTH (pituitary + hypothalamus)
• Sudden steroid withdrawal:
• Dangerous
• Requires gradual tapering

Perfect — I’ll compress everything into a small number of master tables so you get maximum integration + zero omission, without fragmenting logic.

Below tables together cover every single point you listed.

🧠 MASTER TABLE 1 — Adrenal Androgens & Estrogens (Source → Control → Effects → Clinical)

⚙️ MASTER TABLE 2 — Glucocorticoids: Mechanism of Action

🔥 MASTER TABLE 3 — Effects on Intermediary Metabolism

🧩 MASTER TABLE 4 — Permissive Actions of Glucocorticoids (Exam Favorite)

🩸 MASTER TABLE 5 — Vascular, Nervous System & Water Balance Effects

🧬 MASTER TABLE 6 — Blood Cells & Lymphoid Tissue

⚠️ MASTER TABLE 7 — Adrenal Insufficiency vs Excess (Cushing Syndrome)

🧠 MASTER TABLE 8 — Cushing Syndrome: Causes & Effects

🧯 MASTER TABLE 9 — Anti-Inflammatory & Other Actions

⏰ MASTER TABLE 10 — Regulation of Glucocorticoid Secretion

Mineralocorticoids (Aldosterone) — Effects + Mechanisms + Receptor Logic (Zero-Omission)

1) Core actions (what mineralocorticoids DO)

• Main effect: ↑ Na⁺ reabsorption (so ↓ Na⁺ excretion).
• Sites where Na⁺ reabsorption is increased:
• Urine (kidney)
• Sweat
• Saliva
• Colon contents
• Net body effect: Na⁺ retained in ECF → ECF volume expands.
• Kidney target cell: mainly principal cells (P cells) of the collecting ducts.
• Exchange pattern in renal tubules (functional description):
• Under aldosterone, more Na⁺ is “exchanged” for K⁺ and H⁺
• → ↑ K⁺ loss in urine (K⁺ diuresis / kaliuresis)
• → ↑ H⁺ secretion → urine becomes more acidic (↑ urine acidity)

2) Genomic mechanism (classic steroid pathway) — the “10–30 min onward” effect

A) Receptor → nucleus → gene transcription

• Aldosterone binds a cytoplasmic receptor.
• The hormone–receptor complex moves to the nucleus.
• It changes transcription of mRNAs.
• New mRNAs → new proteins → altered cell function.

B) What the aldosterone-stimulated proteins do (2 time scales)

1) Rapid genomic-associated effect (early):

• ↑ activity of ENaC (epithelial sodium channels) by:
• increasing insertion of ENaCs into the apical membrane
• from a pre-existing cytoplasmic pool of channels

2) Slower effect (later):

• ↑ synthesis of ENaCs (more channel production overall)

C) Specific gene highlighted: SGK

• Aldosterone activates gene for serum- and glucocorticoid-regulated kinase (SGK):
• Serine-threonine protein kinase
• An early response gene
• SGK increases ENaC activity (functional upregulation)

D) ENaC subunits transcription

• Aldosterone increases mRNAs for the 3 ENaC subunits (so more channel components made).

E) Why glucocorticoids activating SGK isn’t a “problem”

• SGK can be activated by glucocorticoids too,
• but at mineralocorticoid receptor (MR) sites, glucocorticoids are inactivated locally (details in section 4), so they don’t normally “take over” MR effects.

F) Important nuance: mechanism not fully “settled”

• Aldosterone activates genes for proteins other than SGK and ENaCs
• and inhibits some genes too.
• Therefore, the exact full chain of how aldosterone-induced proteins produce ↑ Na⁺ reabsorption is still not completely resolved.

G) Timing clue supports genomic dominance

• Principal aldosterone effect on Na⁺ transport:
• starts developing in ~10–30 minutes
• peaks later
• This delay pattern strongly suggests dependence on new protein synthesis via genomic mechanisms.

3) Nongenomic / membrane-initiated rapid action (additional evidence)

• Evidence suggests aldosterone can also bind at the cell membrane.
• This can trigger a rapid, nongenomic increase in activity of membrane Na⁺–K⁺ exchangers.
• Result described:
• ↑ intracellular Na⁺
• Likely second messenger:
• IP₃ is “probably” involved (not stated as 100% confirmed).

4) MR vs GR receptor “paradox” + the protective enzyme solution

The puzzle

• In vitro, MR has higher affinity for glucocorticoids than the glucocorticoid receptor (GR) does.
• And in vivo, glucocorticoids are present in large amounts.
• So why don’t glucocorticoids occupy MR in kidney and cause mineralocorticoid-like actions?

The key reason (at least partly)

• Mineralocorticoid-sensitive tissues (esp. kidney) have 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2).

What 11β-HSD2 does (selective “shield”)

• Does NOT affect aldosterone (leaves it active/untouched).
• But converts:
• cortisol → cortisone
• corticosterone → its 11-oxy derivative
• These converted forms (11-oxy derivatives) do not bind the MR.
• So MR stays “available” mainly for aldosterone, preventing glucocorticoid “false mineralocorticoid” effects under normal physiology.

5) Other steroids affecting Na⁺ excretion (relative roles)

• Aldosterone: main mineralocorticoid secreted by adrenals.
• Corticosterone:
• secreted in enough quantity to have a minor mineralocorticoid effect.
• Deoxycorticosterone (DOC):
• secreted in appreciable amounts only in abnormal situations
• has about ~3% of aldosterone’s activity.
• Progesterone and some other steroids:
• in large amounts can cause natriuresis (↑ Na⁺ excretion)
• but little evidence they play a normal physiological role in controlling Na⁺ excretion.

6) Effect of adrenalectomy / adrenal insufficiency (what happens when mineralocorticoids are missing)

A) Electrolyte consequences

• Na⁺ is lost in urine (salt wasting).
• K⁺ is retained → plasma K⁺ rises (hyperkalemia tendency).

B) “Rapid onset” insufficiency → Na⁺ shifts into cells too

• When adrenal insufficiency develops rapidly:
• The amount of Na⁺ lost from ECF exceeds the amount excreted in urine
• → implies Na⁺ is also moving into cells (ECF depletion is bigger than urine loss alone can explain).

C) If posterior pituitary intact (ADH intact)

• Salt loss > water loss
• → plasma Na⁺ falls (hyponatremia tendency).

D) Hemodynamic consequences

• Plasma volume decreases
• → hypotension
• → circulatory insufficiency
• → can progress to fatal shock.

E) Salt replacement helps but usually not enough (species note)

• These changes can be partly prevented by ↑ dietary NaCl.
• Rats can survive indefinitely on extra salt alone.
• But in dogs and most humans, the salt requirement is so huge that:
• it’s nearly impossible to prevent eventual collapse/death
• unless mineralocorticoid treatment is also given.

7) Clinical Box — Apparent Mineralocorticoid Excess (AME)

A) Mechanism

• If 11β-HSD2 is absent or inhibited:
• cortisol is no longer inactivated at MR sites
• cortisol gains strong mineralocorticoid effects by acting on MR
• Syndrome name: apparent mineralocorticoid excess (AME).

B) Clinical picture + labs

• Patients look like hyperaldosteronism clinically (because MR is being activated).
• But aldosterone is LOW, because it’s not the driver.
• Plasma renin activity is LOW as well (suppressed).

C) Causes

• Congenital absence of the enzyme can cause AME.

8) Therapeutic highlight — licorice effect (pseudo-hyperaldosteronism)

• Prolonged ingestion of licorice can ↑ blood pressure.
• “Outside the United States,” licorice contains glycyrrhetinic acid.
• Glycyrrhetinic acid inhibits 11β-HSD2.
• So MR is exposed to cortisol → MR-activated Na⁺ absorption increases.
• Mechanism emphasized:
• ↑ sodium absorption via ENaC in the renal collecting duct
• Outcome:
• blood pressure can rise.

Quick exam-logic chain (one-liner)

• Aldosterone → principal cells (CD) → ↑ ENaC function + ↑ ENaC synthesis (SGK early) → ↑ Na⁺ reabsorption → ECF expansion + ↑ K⁺ loss + ↑ H⁺ secretion → acidic urine; MR protected from cortisol by 11β-HSD2; inhibition/absence → AME; licorice (glycyrrhetinic acid) inhibits 11β-HSD2 → ↑ BP.

🟦 MINERALOCORTICOIDS (ALDOSTERONE) — COMPLETE MASTER TABLE (ZERO-OMISSION)