THE DIAGNOSTIC VALUE OF SODIUM TOLBUTAMIDE IN HYPOGLYCEMIC STATES*†

Abstract

Intravenous sodium tolbutamide tests were performed in patients with (1) proven insulomas, (2) functional hyperinsulinism, (3) mild diabetes mellitus and associated postprandial nypoglycemia, (4) severe adrenal insufficiency, and (5) liver disease. Healthy subjects were used as controls. Administra-tion of sodium tolbutamide to patients with functioning islet-cell adeno-mas usually produced a greater degree of hypoglycemia than was observed in the other subjects studied. Of much greater significance, however, were the prolonged periods of hypoglycemia in the insuloma patients. After removal of the insulomas the response to tolbutamide became normal. Persistence of tolbutamide-induced hypoglycemia: (1) is a valuable adjunct in the diagnosis of insuloma, (2) is due, in part, to release of excessive amounts of insulin from the insuloma, and (3) is supportive evidence that the primary mechanism of action of the sul-fonylureas is release of pancreatic insulin. From a clinical point of view the intravenous tolbutamide test is of greatest value in the differentiation between organic and functional hyperinsulinism.