Zona glomerulosa of the adrenal cortex is the EXCLUSIVE site of aldosterone synthesis because:

• A Aldosterone synthase (CYP11B2) is expressed only in zona glomerulosa; zona fasciculata lacks it ✓
• B It is the only zone expressing ACTH receptors, enabling ACTH stimulation of aldosterone
• C Angiotensin II receptors are absent in zonae fasciculata and reticularis
• D Zona glomerulosa contains the highest 3β-hydroxysteroid dehydrogenase activity

Explanation

Aldosterone synthesis requires the enzyme aldosterone synthase (CYP11B2), which converts corticosterone → 18-hydroxycorticosterone → aldosterone. CYP11B2 expression is restricted to zona glomerulosa. Zona fasciculata expresses CYP11B1 (11β-hydroxylase), which produces cortisol from 11-deoxycortisol but cannot complete aldosterone synthesis. This zonal restriction explains why aldosterone secretion responds primarily to angiotensin II (AT1 receptors abundant in glomerulosa) and K+, while cortisol is ACTH-regulated in fasciculata. ACTH also weakly stimulates glomerulosa but is not its primary regulator.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.