Hyperinsulinemic Hypoglycemia Associated With a Neurofibrosarcoma

Hypoglycemia associated with extrapancreatic tumors is a well known but uncommon phenomenon. The types of tumors associated with hypoglycemia are generally of mesodermal origin (fibrosarcoma, neurofibroma, mesothelioma) but are occasionally endodermal in origin (hepatoma, adrenal carcinoma, renal carcinoma).¹ Various mechanisms regarding the pathogenesis of tumor hypoglycemia have been postulated, including production of insulin or an insulin-like substance by the tumor, consumption of glucose by the tumor mass, or production of a polypeptide or amino acid, particularly tryptophan, causing inhibition of gluconeogenesis.^1-3 Early studies involving nonspecific bioassay techniques demonstrated an increase in "insulin-like activity" in plasma, tumor tissue, or both.^4,5 However, subsequent studies employing the specific immunoassay technique described by Yalow and Berson⁶ have failed repeatedly to provide evidence of hyperinsulinemia associated with extrapancreatic tumor hypoglycemia.^5,7-9 Oleesky et al¹⁰ described hyperinsulinemic hypoglycemia in a patient with a retroperitoneal fibrosarcoma, but their data consisted of a single determination of immunoreactive insulin. In