Simultaneous presentation of an insulinoma and type 2 diabetes mellitus: A case report

Hypoglycemia in the setting of diabetes mellitus is usually ascribed to the management of diabetes mellitus. Rarely, an additional etiology should be considered. We report a 35-year-old woman who presented with both type 2 diabetes mellitus and an insulinoma. She had a history of diet-controlled gestational diabetes and developed symptomatic fasting and nonfasting hypoglycemia immediately postpartum. She presented for evaluation of hypoglycemia 3 months postpartum. The episodes of hypoglycemia occurred during fasting with the lowest documented blood glucose being 2.16 mmol/L (39 mg/dL), but also occurred between meals and at night. Additionally, she also had many glucose values above 11.1 mmol/L (200 mg/dL) meeting the criteria for type 2 diabetes mellitus. A 72-hour fast led to a documented episode of symptomatic hypoglycemia accompanied by elevated insulin levels after 8 hours (glucose 2.3 mmol/L [42 mg/dL], 69.5 pmol/L [insulin 10 μIU/mL]). Abdominal computed tomography and abdominal ultrasound were normal, but pancreatic venous sampling localized a lesion in the distribution of the splenic artery, and intraoperative ultrasound revealed a 1.5-cm mass abutting the splenic artery. She underwent distal pancreatectomy, and pathology and immunohistochemistry showed an insulin-producing neuroendocrine tumor. After surgery, the hypoglycemia resolved and the patient had persistent hyperglycemia. This case describes the simultaneous presentation of both an insulinoma and type 2 diabetes mellitus before resection of the tumor.