Glucose metabolism in a patient with hyperthyroidism and an insulinoma

A 67-year-old woman was admitted in hypoglycemic coma, with fever and signs of hyperthyroidism. Diagnosis was made of both an insulinoma and subacute ("De Quervain") thyroiditis. This rare coincidence of two diseases with opposite effects on serum glucose levels, offered a rare opportunity to study glucose metabolism in this peculiar physiopathological situation. During the day abnormally high postprandial blood glucose levels were seen, pointing to the glucose intolerance usually seen in the hyperthyroid state. During the night and after prolonged fasting, however, hypoglycemia predominated, consistent with the clinical picture typical of an insulinoma. After resection of the insulinoma and spontaneous healing of hyperthyroidism, glucose metabolism reverted to normal. As shown in this case, concurrent hyperthyroidism and an insulinoma may lead to consecutive episodes of glucose intolerance and hypoglycemia within the same 24-hour period.