Insulinoma accompanied by diabetes mellitus.

A 53-year-old type 2 diabetic man was admitted due to spontaneous relatively hyperinsulinemic hypoglycemia. Oral glucose ingestion and arginine tolerance test showed hyperinsulinemic response. Arterial stimulation and venous sampling (ASVS) showed hyperinsulinemic response measured from the splenic artery after calcium gluconate stimulation. Diagnosis was insulinoma in the pancreas feeding from the artery. He has not suffered from spontaneous hypoglycemia since removal of the pancreatic body, tail and spleen. The specimen showed a solitary islet cell tumor. The high homeostasis model assessment of insulin resistance (HOMA-R) levels reflecting insulin resistance and hyperinsulinemic response after operation remained almost unchanged, indicating high insulin resistance and an insulin hypersecreting diabetic patient.