In the management of primary hyperaldosteronism, which biochemical pattern is MOST characteristic of bilateral adrenal hyperplasia (idiopathic hyperaldosteronism) on adrenal vein sampling?

• A Lateralisation ratio >4:1 with aldosterone:cortisol ratio confirming unilateral excess
• B Suppressed aldosterone bilaterally after cosyntropin stimulation
• C No significant lateralisation; bilateral excess aldosterone secretion relative to cortisol ✓
• D Unilateral cortisol excess with contralateral aldosterone suppression

Explanation

In bilateral adrenal hyperplasia, adrenal vein sampling shows that both adrenal veins secrete excess aldosterone relative to cortisol without significant lateralisation (lateralisation ratio <2:1). Lateralisation >4:1 suggests an aldosterone-producing adenoma (Conn's syndrome), which is amenable to unilateral adrenalectomy. Bilateral hyperplasia is treated with mineralocorticoid antagonists (spironolactone or eplerenone), not surgery.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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