Co-existence of insulinoma, non-functional pancreatic neuroendocrine tumor, and parathyroid adenoma in clinically diagnosed MEN1: A case report

Abstract

Insulinoma is a rare functioning neuroendocrine tumor that typically presents with neuroglycopenic or autonomic symptoms due to hypoglycemia. These tumors are uncommon, with an incidence ranging from approximately 1 to 32 million cases per year, and are the most common cause of hyperinsulinemic hypoglycemia in adults. Symptoms usually resolve after glucose administration or postprandial, with typical manifestations occurring during fasting due to excessive insulin secretion. Laboratory evaluations typically reveal elevated insulin and C-peptide levels.

We report a case of a 67-year-old male who presented with behavioral changes and altered consciousness. Initial laboratory investigations revealed hypoglycemia, hypophosphatemia, and hypercalcemia. A parathyroid scan identified a hyperfunctioning parathyroid adenoma. MRI and CT imaging of the upper abdomen revealed Pancreatic Neuroendocrine Tumors (PNETs) in both the distal pancreas (insulinoma) and the pancreatic head (non-functional NET). With two major endocrine tumors, the patient can be clinically diagnosed with MEN1. The patient underwent surgical resection, including distal pancreatectomy and pancreaticoduodenectomy. Postoperatively, the patient developed feeding intolerance and a pancreatic fistula, both of which were managed conservatively. We discuss the diagnostic workup, surgical management, postoperative management, surveillance and review the current literature on the co-existence of insulinomas and non-functional pancreatic neuroendocrine tumors.