Isolated Hypoaldosteronism in Adults

To clarify the mechanism causing isolated hypoaldosteronism in adults, we studied six patients with unexplained hyperkalemia. On a normal sodium intake, excretion of tetrahydrodeoxycorticosterone, tetrahydrocorticosterone, and 17-hydroxycorticoids was normal and increased normally with ACTH stimulation. Excretion of metabolites of aldosterone and 18-hydroxycorticosterone was subnormal or barely normal, and aldosterone excretion failed to respond normally to sodium depletion and ACTH. Plasma renin activity (PRA) and concentration were subnormal and failed to increase normally with upright posture and sodium depletion; furosemide increased PRA in only one patient. Restoration of normal serum potassium with cation exchange resin failed to increase PRA in the three patients studied. Plasma renin substrate was normal or slightly elevated. The patients studied differ from patients with Addison's disease and infants with enzymatic defects in aldosterone biosynthesis in whom PRA is increased. The data su...