Non-Islet Cell Tumor Hypoglycemia Masquerading as Diabetes Remission in a Patient With Type 2 Diabetes Mellitus

Non-islet cell tumor hypoglycemia (NICTH) is a rare paraneoplastic phenomenon of tumor insulin-like growth factor (IGF)-2 hypersecretion. We report a case of a man with poorly controlled diabetes who experienced rapid glycemic improvement after 1 year of oral glucose-lowering therapy. He was diagnosed as achieving diabetes remission after medication cessation. However, he began experiencing recurrent symptomatic hypoglycemia after medication cessation. During a supervised fast, venous glucose dropped to 46.9 mg/dL (SI: 2.6 mmol/L) (reference range, 72.1-140.5 mg/dL [SI: 4.0-7.8 mmol/L]), with suppressed serum C-peptide and insulin, but undetectable beta-hydroxybutyrate levels. Venous glucose rose 37.8 mg/dL (SI: 2.1 mmol/L) (46.9 to 84.7 mg/dL [SI: 2.6 to 4.7 mmol/L]) following intravenous glucagon administration at fast cessation. Serum IGF-1 was low with raised IGF-2, and the IGF-2 to IGF-1 ratio was 33:1, confirming IGF-2 excess. Imaging revealed a large central-lower abdominal mass. He was started on prednisolone and frequent meals to prevent hypoglycemia before tumor resection. Histology revealed a solitary fibrous tumor. Postoperatively, his hypoglycemia resolved. NICTH can complicate glycemic assessment in concomitant diabetes. Clinicians should suspect underlying hypoglycemic disorders in persons with diabetes who develop unexpected glycemic improvement or hypoglycemic episodes despite medication reduction or cessation.