A 46-year-old woman with new-onset hypertension is found to have hypokalemia. Which diagnosis is most likely?

• A. Pheochromocytoma
• B. Renal artery stenosis
• C. Coarctation of the aorta
• D. Primary aldosteronism

Answer: (D)

Excess mineralocorticoid activity best explains both hypertension and low potassium. Aldosterone increases sodium reabsorption in the distal nephron, which expands extracellular fluid and raises blood pressure, while enhancing potassium (and hydrogen) secretion into the urine, leading to hypokalemia and often metabolic alkalosis. In primary aldosteronism, aldosterone is elevated with suppressed renin due to feedback, so the aldosterone-to-renin ratio is high. This pattern fits adrenal adenoma or bilateral adrenal hyperplasia as the cause. Pheochromocytoma would present with episodic catecholamine-related symptoms rather than a classic potassium disturbance. Renal artery stenosis causes secondary hyperaldosteronism with high renin, not suppressed renin. Coarctation causes hypertension without the characteristic hypokalemia.