Primary Hyperaldosteronism

Primary aldosteronism is autonomous aldosterone production, causing hypertension, suppressed renin and often hypokalaemia.

• Prevalence 5 to 10% of hypertensives, 20% of resistant hypertension; the commonest cause of secondary hypertension.
• Causes: bilateral adrenal hyperplasia (60%), aldosterone producing adenoma (35%), unilateral hyperplasia, familial hyperaldosteronism types I (glucocorticoid remediable, CYP11B1/2 chimera), II, III (KCNJ5), IV, adrenal carcinoma.
• Higher cardiovascular, renal and metabolic complications than essential hypertension.

• Resistant or early onset hypertension, hypertension with hypokalaemia (only 30%), adrenal incidentaloma, obstructive sleep apnoea, atrial fibrillation, family history of early stroke.
• Muscle weakness, cramps, polyuria, headache.
• No oedema.

• Screen with aldosterone to renin ratio (ARR) in the morning, correct potassium to above 4.0, stop mineralocorticoid antagonists for 4 to 6 weeks if safe; positive if aldosterone over 10 ng/dL (280 pmol/L) and ARR over 20 to 30 with suppressed renin.
• Confirmatory test: saline infusion test (2 L over 4 hours, aldosterone above 10 ng/dL after infusion, below 5 excludes), oral salt loading, captopril challenge, or not needed when spontaneous hypokalaemia, undetectable renin, aldosterone over 20 ng/dL.
• Adrenal CT; adrenal vein sampling for subtype in candidates for surgery (lateralisation index over 4), unnecessary in under 35 with spontaneous hypokalaemia and a CT adenoma.
• Genetic testing for familial forms in young patients.

• Unilateral disease: laparoscopic adrenalectomy (cure of hypertension in 30 to 60%, hypokalaemia in nearly all); continue antihypertensives, monitor potassium and creatinine postoperatively (hypoaldosteronism may cause hyperkalaemia).
• Bilateral or non surgical: mineralocorticoid receptor antagonist spironolactone 12.5 to 25 mg daily titrated to 100 mg (titrate to renin unsuppressed), or eplerenone 25 to 50 mg twice daily; add amiloride, ACE inhibitor, calcium channel blocker as needed. Target potassium above 4.0 and renin unsuppressed.
• Glucocorticoid remediable aldosteronism: dexamethasone 0.25 to 0.5 mg at night or prednisolone 2.5 to 5 mg.
• Monitor potassium, creatinine, blood pressure; spironolactone side effects (gynaecomastia, menstrual disturbance).