[Primary aldosteronism in resistant hypertension unmasked by a thiazide-induced severe hypokalaemia].

Primary aldosteronism is the most common cause of secondary hypertension but remains frequently underdiagnosed in primary care. We report a 71-year-old man with resistant hypertension and low-normal serum potassium in whom a minimal increase in hydrochlorothiazide dosage (12.5 to 25 mg) precipitated severe hypokalaemia (1.6 mmol/L), metabolic alkalosis, and rhabdomyolysis. An office electrocardiogram showed hypokalaemia-related changes, prompting urgent referral to the emergency department. Further evaluation revealed an elevated aldosterone-to-renin ratio and a left adrenal nodule, supporting the diagnosis of primary aldosteronism. This case highlights the importance of recognizing a disproportionate hypokalaemic response to thiazide treatment as a potential indicator of underlying primary aldosteronism. It also underscores the role of family physicians in early detection through appropriate screening.