Doege-Potter Syndrome: A Solitary Fibrous Tumor Causing Non-Islet Cell Tumor Hypoglycemia

Doege-Potter syndrome occurs when incompletely processed insulin-like growth factor 2 (IGF-2), also known as big IGF-2, is produced by a solitary fibrous tumor (SFT) and results in non-islet cell tumor hypoglycemia (NICTH). We discuss here the case of a 66-year-old male who presented with a 2-week history of increasing confusion and a serum glucose of 34 mg/dL. The patient's symptoms immediately improved with dextrose. The patient did not use insulin, serum sulfonylurea screen was negative, and testing for adrenal insufficiency was unremarkable. Outpatient laboratory evaluation revealed a serum glucose of 48 mg/dL along with low insulin, C-peptide, and proinsulin levels. Further work-up showed an IGF-2 to IGF-1 ratio of 38:1. A ratio greater than 10:1 is diagnostic of NICTH. Imaging demonstrated a 21-cm mass in the lower abdomen and pelvis. The patient underwent surgical resection. The hypoglycemia resolved immediately postoperatively. Surgical pathology revealed a malignant SFT. In NICTH, big IGF-2 forms a complex that is biologically active and saturates the insulin and IGF receptors, resulting in refractory hypoglycemia. Although glucocorticoids can mitigate hypoglycemia, complete surgical resection is the only definitive treatment of NICTH. This case highlights the importance of maintaining a broad differential for seemingly simple hypoglycemia.