New findings in apparent mineralocorticoid excess.

We report two female siblings (ages 4 and 9 years) and one 8-year-old male with the syndrome of apparent mineralocorticoid excess (AME) presenting with low renin hypertension and hypoaldosteronism. The deficiency of 11 beta-hydroxysteroid dehydrogenase results in a defect of the peripheral metabolism of cortisol (F) to cortisone (E). As a result, the serum cortisol half-life (T1/2) is prolonged, ACTH is suppressed, and serum F is normal. The specific diagnosis of the disorder was made by the decreased ratio of the urinary metabolites of E (tetrahydrocortisone, THE) and F (tetrahydrocortisol, THF). Continuous i.v. hydrocortisone administration caused an increase in blood pressure and decrease in serum potassium demonstrating the abnormal mineralocorticoid activity of cortisol in these patients. Addition of spironolactone resulted in a decrease in blood pressure, rise in serum potassium and a gradual increase in plasma renin activity. These studies suggest that an abnormality in cortisol action or metabolism results in cortisol behaving as a potent mineralocorticoid and causing the syndrome of AME.