An unusual beta-cell adenoma.

An unusual case of insulinoma in a 51-year-old man demonstrates the difficulties in diagnosing and treating hypoglycemia. From the many laboratory tests and procedures performed, the only findings typical of insulinoma were inappropriate values of plasma immunoreactive insulin in relation to the corresponding values of blood glucose, and these were sporadic. A small beta-cell adenoma in the pancreatic head was the cause of the hypoglycemia.