Hypoglycemia, Something Lost in Translation

Abstract

Introduction: Insulinoma is a rare neuroendocrine tumor that may occur sporadically or as part of multiple neuroendocrine neoplasia type 1, with an incidence of 4 per million per year. Given the nonspecific symptoms of hypoglycemia, the diagnosis of insulinoma may be delayed by months, years or even decades. Case Presentation: A 50 year-old Hispanic, Spanish speaking male with a history of hypertension presented with progressive epigastric pain, nausea and bilious vomiting for 2 days. Physical exam was notable for abdominal distention and tenderness. Initial labs showed white blood cells of 19.4 k/uL (4-10.8), glucose of 85 mg/dl (65-140). CT abdomen showed findings consistent with moderate grade small bowel obstruction and normal pancreas. The patient was managed conservatively with nasogastric tube placement and nothing per oral (NPO). Within 8 hours started experience sweating, restlessness, fingerstick glucose was 40 mg/dl. Upon questioning, he reported episodes of lightheadedness, sweating and shakiness 8 years prior to this hospitalization, and he recalled being told that he was hypoglycemic during prior hospitalizations at another institution. He stated he was told to drink juice upon experiencing such symptoms and no work up or diagnostic investigation was recommended. We initiated a hypoglycemia investigation when he was NPO, when serum glucose level of 40 mg/dl. Labs showed insulin level 34 uIU/mL (3-19), free insulin 25 uIU/mL (3-19), C-peptide 3.32 ng/mL (0.81-3.85), beta hydroxybutyrate <0.02 mmol/L (0.02-0.27) and proinsulin of 36.6 pmol/L (3-50) and hemoglobin a1C of 5% (3.8-5.6). Serum screening for hypoglycemic agents was negative. When MRI abdomen was negative for a pancreatic mass. We proceeded with advanced diagnostic imaging with endoscopic ultrasound (EUS) which showed a 26 mm x 19 mm ovoid, hypoechoic mass at the junction of the pancreatic body and tail. Tissue specimen obtained with fine needle aspiration showed grade 1 neuroendocrine neoplasm. The patient underwent distal pancreatectomy and splenectomy with suture repair of the small bowel and left wedge liver biopsy. The pathology showed a well-differentiated neuroendocrine tumor of the pancreas, positive for synaptophysin, chromogranin and CD56 and Ki-67 with proliferation index <2% and no evidence of metastasis to the liver. The patient’s hypoglycemia resolved following surgery and rose to > 200 mg/dL requiring us to begin insulin therapy during the hospital stay before ultimately discharging the patient on metformin for type 2 diabetes. Conclusion: Insulinoma is a rare but treatable neuroendocrine tumor. Early diagnosis is important to avoid adverse clinical events related to hypoglycemia. It is important to maintain a strong clinical suspicion in order to identify and pursue the cause of unexplained hypoglycemia to improve the quality of life of patients with this rare condition.