Which part of the adrenal gland secretes aldosterone?

Aldosterone Secretion in the Adrenal Gland

Aldosterone is secreted by the zona glomerulosa of the adrenal cortex. 1, 2

Anatomy and Physiology of Aldosterone Production

• The zona glomerulosa is the outermost layer of the adrenal cortex and is specifically responsible for the synthesis and secretion of aldosterone 2, 3
• Aldosterone production in the zona glomerulosa is independent of the renin-angiotensin system in certain conditions and may not be suppressible with dietary sodium loading 1
• Due to the lipophilic nature of aldosterone, it is not stored in vesicles but rather synthesized and secreted immediately upon cell stimulation 4

Regulation of Aldosterone Secretion

• Aldosterone secretion is primarily regulated by:

  • The renin-angiotensin II system 2, 4
  • Serum potassium levels (hyperkalemia) 2, 4
  • Adrenocorticotropic hormone (ACTH) 3

• The signaling pathway for aldosterone production involves:

  • Activation of AT1 receptors by angiotensin II 4
  • Increased intracellular calcium concentration through voltage-gated calcium channels 5
  • Activation of StAR protein, which catalyzes the rate-limiting step in aldosterone biosynthesis 4

Clinical Significance

• Excessive aldosterone production from the zona glomerulosa can lead to:

  • Hypertension due to sodium retention and expanded extracellular fluid volume 2
  • Hypokalemia from increased potassium excretion 2
  • End-organ damage to kidneys and heart 3

• Primary aldosteronism (Conn syndrome) is characterized by:

  • Elevated aldosterone levels with suppressed renin activity 2
  • Aldosterone-to-renin ratio typically greater than 30 2
  • Often associated with adrenal adenomas in the zona glomerulosa 1, 2

Diagnostic Considerations

• Diagnosis of aldosterone-producing adenomas involves:
  • Measuring plasma aldosterone and renin activity 2
  • Confirmatory testing with saline suppression or salt loading tests 1, 2
  • Adrenal imaging to identify adenomas 1, 2
  • Adrenal vein sampling to confirm lateralization of aldosterone production 1

Treatment Approaches

• For aldosterone-producing adenomas:
  • Laparoscopic adrenalectomy is the treatment of choice for unilateral adenomas 1, 2
  • Medical management with mineralocorticoid receptor antagonists is used for bilateral disease or non-surgical candidates 2

Clinical Pitfalls

• Normokalemic primary aldosteronism is more common than previously recognized and may be missed if hypokalemia is used as the sole screening criterion 6
• Non-aldosterone mediated mineralocorticoid excess can mimic the features of hyperaldosteronism and should be considered in the differential diagnosis 6
• The zona glomerulosa may have multiple functions beyond aldosterone synthesis, which could explain some inconsistencies in clinical presentations 7