The therapeutic effect of a new angiotensin-converting enzyme inhibitor, enalapril maleate, in idiopathic hyperaldosteronism.

Patients with idiopathic hyperaldosteronism (IHA) manifest hypertension, hypokalemia, and renin suppression. IHA is thought to have one of three possible etiologies: zona glomerulosa autonomy, an aldosterone secretory factor, or angiotensin-II (A-II) adrenal hypersensitivity. To determine the contribution of A-II adrenal hypersensitivity in IHA, four patients with IHA were treated with a new angiotensin-converting enzyme inhibitor, enalapril, on a controlled diet (sodium [128 mEq/day] and potassium [80 mEq/day]) in a metabolic unit. The results of this study demonstrate that enalapril therapy in three of four patients normalized blood pressure, improved potassium balance, elevated PRA, reversed the postural increment in plasma aldosterone concentration (PAC), and reduced aldosterone secretion to normal. The fourth patient with bilateral macronodular disease, on the other hand, had no improvement in any of the above indices, despite maximal doses of enalapril (80 mg/day). This patient, however, may have had bilateral adrenal adenomas, based on extremely elevated 18-OH-corticosterone levels (greater than 100 ng/dl), and because of a lack of adrenal A-II hypersensitivity, demonstrated by a fall in pre-enalapril, postural-, and lasix-induced PAC. In conclusion, enalapril improved the hypertension, hypokalemia, renin suppression, and hyperaldosteronism in three patients with IHA over 28 days of therapy. The results of this study suggest an etiologic role of A-II adrenal hypersensitivity in IHA.