Acquired Partial Corticosterone Methyl Oxidase Type II Defect in Diabetes Mellitus: Case of Hyperreninemic Hypoaldosteronism

The aim of this study was to investigate the pathogenesis of hypoaldosteronism in diabetes. Endogenous elevation of plasma renin activity and exogenous corticotropin were used to study steroidogenesis. Observations were made over 12 yr on the evolution and treatment of hyperkalemia in a diabetic subject. In 1977, potassium, baseline cortisol, aldosterone, and renin activity were normal; renin activity increased normally with posture; and cortisol responded normally to ACTH infusion. Nine yr later, persistent hyperkalemia was documented. Upright renin activity was elevated to 5.26 ng · L⁻¹ · s⁻¹, with concomitant elevation of 18-hydroxycorticosterone (18-OHB) and a low-normal aldosterone level. One hour after administration of 0.25 mg i.m. cosyntropin, cortisol increased normally, aldosterone increased from 220 to 360 pM, and 18-OHB increased from 3700 to 4800 pM. During treatment with fludrocortisone, fludrocortisone with furosemide, and furosemide alone, improvement of hyperkalemia was noted. Endogenous hyperreninemia and basal elevations of 18-OHB, accompanied by limited aldosterone responsiveness to renin and ACTH, suggest the presence of a partial corticosterone methyl oxidase type II defect. Evolution of hyperkalemia between 1977 and 1986 suggests this defect was acquired.