SUN-034 A Case of an Insulinoma

Abstract Disclosure: O. Onwudiwe: None. A.M. Aviles Melendez: None. K.Z. Win: None. Background: Insulinoma is a rare neuroendocrine tumor (NET) causing hypoglycemia due to inappropriate insulin secretion. These tumors arise from ductular or acinar pancreatic cells rather than islet cells. Insulinomas primarily cause fasting hypoglycemia, though postprandial hypoglycemia can occur. Diagnosis relies on biochemical testing and imaging. Surgical resection is the first-line treatment, offering a potential cure. Pharmacological or non-surgical therapies become essential when surgery is delayed or not feasible. This case highlights the challenges of managing insulinoma when surgery is not immediately possible. Case: A 65-year-old woman with class 3 obesity and anxiety presented with recurrent episodes of disorientation, confusion, shakiness, and occasional loss of consciousness, primarily in the fasting state. Symptoms resolved with food intake, leading to weight gain from frequent eating. She had no history of diabetes or gastric bypass surgery. Her presentation met Whipple’s triad criteria. Biochemical evaluation confirmed endogenous hyperinsulinism, suggestive of insulinoma. Imaging showed a cystic lesion in the posterior pancreatic head, though endoscopic ultrasound failed to locate it. Initial treatments with calcium channel blockers and lanreotide were ineffective. She began diazoxide therapy and awaits repeat endoscopic ultrasound and planned surgery. Discussion: Surgical resection, including enucleation or distal pancreatectomy, is the gold standard for insulinoma, with high cure rates. However, some lesions are not detectable on imaging or endoscopic ultrasound, complicating surgical decisions. In such cases, pharmacological therapy is critical. Diazoxide, the only FDA-approved treatment for endogenous hyperinsulinism, is the first-line medication. A 2021 meta-analysis of six cohort studies with 1,142 participants reported a 71% response rate to diazoxide. Somatostatin analogs (e.g., octreotide, lanreotide) are second-line treatments, inhibiting insulin secretion by activating somatostatin receptors, particularly in malignant cases. Non-surgical ablative methods, such as ethanol ablation, radiofrequency ablation, and high-intensity focused ultrasound, offer alternatives for patients unfit for surgery. A review found an 84% success rate over 16 months, with a recurrence rate of 16% and transient adverse effects in 23%. Ethanol and radiofrequency ablation were the most effective. Conclusion: Insulinomas, though rare, are the leading cause of non-diabetic hypoglycemia due to endogenous hyperinsulinism. Surgical resection is the definitive treatment. Diazoxide and somatostatin analogs provide effective management when surgery is delayed or contraindicated. Non-surgical techniques show promise but require further research to refine treatment protocols and improve long-term outcomes. Presentation: Sunday, July 13, 2025