A Rare Cause of Hypoglycemia in a Diabetic Patient Malign Metastatic Insulinoma

The occurrence of metastatic insulinoma in a patient with pre-existing diabetes is extremely rare. We report the case of a diabetic patient who had frequent hypoglycemic episodes, apparently related to metastatic insulinoma. A 47-year-old woman with type 2 diabetes mellitus who had been treated with a sulfonylurea for 10 years began experiencing frequent episodes of hypoglycemia even after complete withdrawal of the hypoglycemic agent. Endogenous hyperinsulinism was found using a prolonged fasting test. Computed tomography identified a pancreatic tumor with metastatic liver lesions and peripancreatic lymphadenopathies. Ultrasound-guided hepatic mass biopsy was performed and the pathology examination of the tumor demonstrated a neuroendocrine tumor. The patient refused surgery; octreotide (10mg) was administered. A few days later, the patient had no further episodes of hypoglycemia. Although the coincidence of insulinoma and diabetes is extremely rare, after excluding common reasons for hypoglycemia in diabetic patients, insulinoma must be considered.