A 48-year-old man with recurrent severe fasting hypoglycemia has suppressed insulin and C-peptide levels despite low glucose. Imaging shows a large left-sided intrathoracic mass attached to the pleura. The paraneoplastic mechanism responsible is secretion of:
- A Insulin by ectopic pancreatic tissue within the mass
- B Insulin-like growth factor 2 (big IGF-2) by the tumor ✓
- C Glucagon-like peptide causing reactive hyperinsulinemia
- D Antibodies against the insulin receptor mimicking insulin action
Correct answer: B. Insulin-like growth factor 2 (big IGF-2) by the tumor
Explanation
Solitary fibrous tumor of the pleura (formerly fibrous mesothelioma) and some other mesenchymal tumors secrete incompletely processed big IGF-2, which activates insulin receptors and produces non-islet cell tumor hypoglycemia known as the Doege-Potter syndrome. Suppressed insulin and C-peptide exclude endogenous hyperinsulinism. Option A is anatomically implausible, and option D describes type B insulin resistance, an autoimmune disorder unrelated to thoracic tumors.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.