Is Extrapancreatic Tumor Hypoglycemia Associated with Elevated Levels of Insulin-Like Growth Factor II?*

Abstract

We have tried to answer the still controversial question of whether or not extrapancreatic tumor hypoglycemia is associated with elevated levels of insulin-like growth factor II (IGF II), keeping in mind that controversial results may be due to methodological differences. Serum levels of IGF II were determined by a rat liver membrane radioreceptor assay and by RIA. Serum samples were gel filtered at acidic pH, and some sera were also tested after acidethanol extraction as an alternative method for dissociating and separating IGF from the IGF carrier protein. Additionally, the radioreceptor assay was performed with a labeled partially purified IGF preparation [nonsuppressible insulin-like activity soluble in acid-ethanol (NSILA-s “70”)] that was used by a group reporting elevated NSILA-s levels in about 40‰ of their patients with tumor hypoglycemia. Mean serum levels of receptor-reactive IGF II and immunoreactive IGF II (±SD) were 436 ±169 and 540 ± 256 ng⁄ml in 22 patients with tumor hypoglycemia, as compared with 578± 155 and 647 ± 217 ng⁄ml in 28 normal adults. This pattern of slightly, but not significantly lower mean IGF II values in tumor hypoglycemia was unchanged when a less pure IGF preparation (NSILA-s 70) was used as a tracer or when the sera were extracted with acid-ethanol. Thus, hypoglycemia resulting from extrapancreatic tumors is not likely to be associated with increased receptorreactive or immunoreactive IGF II levels. (J Clin Endocrinol Metab55: 833, 1982)