SUN-315 Ketogenic Diet Unmasking a Case of Insulinoma

Background: Insulinoma is a rare, sporadic neuroendocrine tumor, with incidence of 4 cases per million people (1). It is often difficult to diagnose given presentation of vague symptoms and often lack of localization of tumor on initial imaging. Timely diagnosis is usually necessary as there is commonly total resolution with surgery. We present a unique case of ketogenic diet unmasking insulinoma in a young healthy male. Clinical Case: An obese otherwise healthy 47-year male presented to our institution with rapid onset altered mental status followed by syncope and witnessed seizure-like activity. He denied previous episodes, although recalled symptoms of diaphoresis and confusion at night since beginning the ketogenic diet one week prior. Initial evaluation demonstrated normal metabolic panel, thyroid function, cortisol level, and HbA1C value of 4.8%, however plasma glucose level was 30 mg/dL with a corresponding insulin level to 87.9 (2.6-24.9) mlU/mL. Initial trauma protocol CT did not reveal injuries and the pancreas appeared normal. Hypoglycemia resolved initially following dextrose administration, however, he had several repeat episodes of symptomatic hypoglycemia despite continuous IV dextrose infusion and eating an oral diet. Two hours into 72 hour fasting test, he developed symptoms of neuroglycopenia, glucose level of 38 mg/dl with insulin level of 76.6 mlU/mL and C-peptide level of 6.7 ng/mL (1.1-1.4 ng/mL). MRI abdomen revealed 2.2x1.5 cm T2-hyperintense, hypervascular lesion in the pancreatic body with restricted diffusion, compatible with neuroendocrine tumor. Endoscopic ultrasound was completed for surgical planning. Diazoxide was initiated while awaiting surgery. He underwent successful enucleation of solitary pancreatic head lesion with resolution of episodic hypoglycemia. Histopathology confirmed neuroendocrine tumor, immunostaining positive for insulin. Conclusion: While clinicians have used ketogenic diet in aiding patients with epilepsy, the recent trend of this very low carbohydrate, high-fat diet for weight loss has been controversial. Insulinoma can be a diagnostic challenge, given the typical clinical presentation is a prolonged course of vague symptoms. Our case is atypical given the rapid onset of symptoms, diagnosis and appropriate treatment within two weeks of starting ketogenic diet. Reference: (1) Mathur, A, et al. “Insulinoma”. Surg Clin North Am. 89.5. (2009)