Insulin-like growth factors in patients with nonislet cell tumors and hypoglycemia.
Insulin-like growth factors (IGF) in serum from 3 patients with nonislet cell tumors and hypoglycemia were measured by radioimmunoassay and by means of a rat liver membrane assay (specific for IGF II). The concentration of IGF II by receptor assay was greater than normal when the samples were initially assayed, but subsequently decreased 48% to 80% over the next 8 to 15 weeks. In the same serum samples, concentrations of both IGF I and IGF II by radioimmunoassay were consistently less than normal. In all 3 patients growth hormone (GH) responses to intravenous arginine were depressed and in 2 of the 3 patients, a GH-dependent 150 K serum protein carrier of IGF was absent. None of these abnormalities were seen in 7 patients with insulinomas and chronic hypoglycemia. The data suggest that some patients with nonislet cell tumors and hypoglycemia produce a receptor-active, nonimmunoreactive IGF-II-like material. This material appears (a) more labile than normal IGF II and (b) capable of inhibiting GH secretion. The latter effect may decrease immunoreactive IGF I and II, as well as decrease the GH-dependent 150 K protein carrier of these factors. The extreme lability of the IGF-II-like material produced by tumors probably explains the previous contradictory reports on this topic.
T J
TJ
Merimee
D001120:Arginine / Q000494:pharmacology; D002352:Carrier Proteins / Q000032:analysis; D006801:Humans; D007003:Hypoglycemia / Q000097:blood*; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000097:blood*; D007335:Insulin-Like Growth Factor II / Q000097:blood*; D009369:Neoplasms / Q000097:blood*; D011956:Receptors, Cell Surface / Q000032:analysis; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000097:blood*
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D001120:Arginine