[A case of hyporeninemic hypoaldosteronism improved by dexamethasone treatment].

A 76-year-old man was admitted because of general fatigue and lumbago. Two years before admission, hyponatremia and hyperkalemia were pointed out, subsequently hydrocortisone (20 mg/day) was given under the diagnosis of panhypopituitarism. The marked improvement was found in the electrolytes abnormality. On examination at admission, there was no abnormality of anterior pituitary function. In addition to the extremely low level of plasma renin activity and aldosterone concentration, the persistent microhematuria and hyperuricemia were found, however, renal histology only showed the benign arteriosclerosis but no significant alteration in juxtaglomerular apparatus and glomeruli. The urinary prostacyclin metabolite output was rather increased compared to that of normal subject, suggesting that prostaglandins may not be responsible for the defect of renin secretion. Although, the cause was still unknown, small dose of dexamethasone was extremely effective to resolve electrolytes abnormality and hematuria.