Which biochemical profile favors a diagnosis of primary aldosteronism over secondary hypertension?

• A. Hyperkalemia with high renin
• B. Hypokalemia with metabolic alkalosis and suppressed renin
• C. Normal potassium with normal renin
• D. Hyponatremia with increased renin

Answer: (B)

Primary aldosteronism causes autonomous aldosterone production that expands extracellular fluid and suppresses the renin-angiotensin system. The excess aldosterone increases NaCl reabsorption while driving potassium and hydrogen ion loss in the distal nephron. This combination yields hypokalemia and metabolic alkalosis, with renin being suppressed due to negative feedback from the expanded blood volume. That specific pattern—low potassium, metabolic alkalosis, and suppressed renin—most strongly points to primary aldosteronism rather than secondary hypertension, where renin would typically be elevated and potassium changes less characteristic.