[Recurrent hypoglycemia in the insulin autoimmune syndrome]

A 72-year-old man with recurrent hypoglycaemia was suspected of having an insulinoma. But several diagnostic methods (computed tomography; mesenteric and coeliac angiography; sella imaging) did not reveal any tumour. 72-hour hunger test did not precipitate any spontaneous hypoglycaemia. A falling insulin-glucose ratio spoke against an insulin-producing tumour. Reactive symptomatic hypoglycaemia occurred 4.5 hours after an oral glucose test. Measurement of insulin concentration demonstrated a slow but pronounced increase (3500 microU) over an already raised initial value (816 microU/ml), typical of prediabetic metabolic regulation. Demonstration of insulin autoantibodies confirmed the diagnosis of an insulin autoimmune syndrome, which has a good prognosis. The patient became free of symptoms on a regimen of frequent small, carbohydrate-poor but fat and bulk-rich meals. Hypoglycaemia recurred when the diet was not observed.