Clinical meaning
Conn syndrome (primary hyperaldosteronism) is excessive aldosterone production independent of the renin-angiotensin system, most commonly from a unilateral aldosterone-producing adenoma (35%) or bilateral adrenal hyperplasia (60%). Aldosterone acts on the mineralocorticoid receptor in the principal cells of the collecting duct, upregulating ENaC (epithelial sodium channel) and Na+/K+-ATPase, causing sodium reabsorption with potassium and hydrogen ion secretion. This produces: hypertension (volume expansion from sodium retention), hypokalemia (potassium wasting), and metabolic alkalosis (hydrogen ion secretion). The elevated aldosterone suppresses renin (via negative feedback from volume expansion), creating the characteristic LOW renin, HIGH aldosterone pattern. Primary hyperaldosteronism is far more common than previously recognized, affecting 5-10% of all hypertensive patients and up to 20% of those with resistant hypertension.
Diagnosis & workup
Diagnostics & workup: - Screening: aldosterone-to-renin ratio (ARR); positive screen if ARR >30 with aldosterone >15 ng/dL - Pre-test preparation: hold spironolactone and eplerenone for 4-6 weeks; hold ACEi/ARB, beta-blockers, dihydropyridine CCBs for 2 weeks if possible; use alpha-blockers and verapamil (minimal RAAS effect) for BP control during testing - Confirmatory testing: oral sodium loading test (3 days high-sodium diet → 24-hr urine aldosterone >12 mcg/day confirms), or IV saline infusion test (2L NS over 4 hours → aldosterone >10 ng/dL confirms), or fludrocortisone suppression test - Subtype differentiation: adrenal CT (identify adenoma vs hyperplasia; note: nonfunctioning incidentalomas are common); adrenal vein sampling (AVS) = gold standard to lateralize aldosterone source before surgery - Adrenal vein sampling: required before surgical decision; lateralization ratio >4:1 indicates unilateral source amenable to adrenalectomy