MON-088 - Biochemically Confirmed Endogenous Hyperinsulinemic Hypoglycemia with Nonlocalizing CT/MRI: Diazoxide as Prolonged Therapy during Ongoing Localization

Background: Localization of insulinomas can be difficult when cross-sectional imaging is unrevealing despite biochemical evidence of endogenous hyperinsulinemic hypoglycemia.

Case: A 25-year-old man with no significant past medical history was admitted for persistent, recurrent level 3 hypoglycemia complicated by rhabdomyolysis, requiring continuous intravenous dextrose. During supervised fasting hypoglycemia (glucose 51 mg/dL), insulin was 11.0 µU/mL, C-peptide 1.69 ng/mL, and proinsulin 45.1 pmol/L, with suppressed beta-hydroxybutyrate (0.12 mmol/L) and HbA1c 4.6%, consistent with endogenous hyperinsulinemic hypoglycemia. An outside hospital reportedly identified an approximately 1 cm pancreatic body lesion; however, repeat multiphasic contrast CT of the chest/abdomen/pelvis and abdominal MRI with and without contrast showed a normal-appearing pancreas without a discrete mass or focal enhancement.

Management/Outcome: The biochemical profile supported continued concern for insulinoma despite nonlocalizing CT/MRI, and a delay before definitive localization and treatment was anticipated. Diazoxide 200 mg twice daily stabilized glycemia, allowed discontinuation of intravenous dextrose, and supported recovery from rhabdomyolysis. The patient tolerated diazoxide during hospitalization without edema, hypotension, or clinically significant gastrointestinal adverse effects, permitting continuation as outpatient medical therapy while further diagnostic evaluation was arranged. Inpatient endoscopic ultrasound (EUS) was unavailable; urgent outpatient EUS and multidisciplinary endocrinology–gastroenterology follow-up were scheduled, with diazoxide continued to prevent recurrent severe hypoglycemia.

Conclusion: Biochemically confirmed endogenous hyperinsulinemic hypoglycemia warrants continued insulinoma-directed evaluation even when CT and MRI fail to localize a lesion. Diazoxide may function as bridging therapy and, when necessary, be continued to maintain euglycemia and reduce hypoglycemia-related morbidity while localization and definitive treatment are pursued.

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