For suspected primary aldosteronism (Conn's syndrome) causing secondary hypertension, which test is most useful for identifying the condition?

• A. Chest x-ray
• B. Renal scan
• C. Serum electrolytes
• D. Urinalysis for metanephrines

Answer: (C)

Understanding that Conn's syndrome causes secondary hypertension through excess aldosterone helps explain the best initial test. Aldosterone stimulates sodium reabsorption and potassium excretion in the distal nephron, which commonly produces hypokalemia and a metabolic alkalosis. Seeing these electrolyte disturbances on a serum electrolyte panel provides a strong clue that aldosterone excess is at play, making serum electrolytes the most useful initial test among the options.

If the electrolytes show low potassium with metabolic alkalosis in a hypertensive patient, the next step is a focused hormonal workup to confirm primary hyperaldosteronism, typically starting with measuring aldosterone and renin levels (aldosterone-to-renin ratio) and then performing confirmatory suppression tests and imaging as needed.

Chest X-ray isn’t a diagnostic tool for primary aldosteronism. A renal scan isn’t used to identify it. Urinalysis for metanephrines targets pheochromocytoma, not aldosterone-mediated hypertension.