Insulinoma induced hypoglycemia in a type 2 diabetic patient.

Insulinoma in a patient with pre-existing diabetes mellitus is extremely rare. We report a case of an insulinoma in a patient with type 2 diabetes mellitus who after 14 years of sulfonylurea treatment experienced recurrent episodes of hypoglycemia. Endogenous hyperinsulinism was confirmed and endoscopic ultrasonography identified a pancreatic tumor, which was positive for insulin by immuno-histological staining. After surgical excision of the tumor, no further hypoglycemic attacks occurred. Loss of body weight after removal of the tumor correlated with a dramatic reduction of insulin resistance to such a degree that diet alone proved sufficient for satisfactory glycemic control.