When hypoglycemia unmasks malignancy: A metastatic insulinoma presenting with recurrent hypoglycemia
Abstract
Background: Spontaneous hypoglycemia in non-diabetic adults is an uncommon clinical entity. Endogenous hyperinsulinism caused by a metastatic pancreatic neuroendocrine tumor (malignant insulinoma) represents a rare and critical diagnosis requiring prompt identification and medical stabilization when surgical cure is precluded. Case summary: A 63-year-old non-diabetic, hypertensive male presented with a 3-year history of recurrent severe neuroglycopenic and adrenergic hypoglycemic episodes occurring primarily in the fasting state. The patient reported marked hyperphagia with a weight gain of 20 kg over 9 months. Laboratory evaluation confirmed endogenous hyperinsulinemic hypoglycemia, with significantly elevated fasting serum insulin (100.24 mU/mL) and C-peptide (6.43 ng/mL) levels corresponding to a documented blood glucose of 2.5 mmol/L. Endoscopic ultrasound (EUS) identified a 3.0 cm × 3.1 cm hypoechoic mass in the pancreatic head/uncinate process, and EUS-guided biopsy confirmed a pancreatic neuroendocrine tumor. Pre-operative magnetic resonance imaging (MRI) with magnetic resonance cholangiopancreatography (MRCP) subsequently revealed multiple liver metastases. Due to advanced distant metastasis, surgical resection was deemed non-viable, and the management strategy was pivoted to long-term medical therapy. Oral Diazoxide (50mg TID) was initiated, successfully stabilizing his blood glucose levels. Conclusions: Evaluation of recurrent fasting hypoglycemia accompanied by marked weight gain should raise high clinical suspicion for endogenous hyperinsulinism. While EUS provides excellent local visualization and biopsy capability for primary pancreatic lesions, complete staging with cross-sectional imaging (MRI/MRCP) is vital to identify hepatic metastases. In unresectable or metastatic insulinomas, medical management with Diazoxide remains the primary therapeutic intervention to control life-threatening hypoglycemia. [J Assoc Clin Endocrinol Diabetol Bangladesh, 2026;5(Suppl 1): S74]