Calcium-channel blockade can mask the diagnosis of Conn's syndrome.

A 30-year-old woman presented with hypertension and hypokalaemia, and was found to have primary aldosteronism due to a Conn's adenoma, whose removal cured the hypertension. Before surgery, the characteristic biochemical changes which enabled the diagnosis were completely masked by administration of a calcium-channel blocker, amlodipine. It is likely that widespread use of this class of drugs contributes to under-diagnosis of Conn's syndrome as a curable cause of hypertension.