Serum insulin-like growth factor II in 44 patients with non-islet cell tumor hypoglycemia

Serum insulin-like growth factor II (IGF-II) was characterized by radioimmunoassay and Western immunoblot in 44 patients with non-islet cell tumor hypoglycemia (NICTH). 31 of 44 patients with NICTH had big IGF-II in sera. When the presence of IGF-II in tumors from 20 patients was investigated, IGF-II in tumors was detected in 18 patients and these patients had big IGF-II in sera. In two patients whose tumors did not contain IGF-II, big IGF-II in sera was not detected. In six patients with IGF-II in tumors, hypoglycemia disappeared and the big IGF-II decreased after successful removal of the tumors. These data indicate that the big IGF-II could be related to hypoglycemia, and that the increased serum big IGF-II suggests IGF-II-producing NICTH. Serum IGF-II levels in 31 patients with big IGF-II were greater than those in 13 patients without it (Mean +/- SEM: 723+/-54 vs. 326+/-31 ng/ml), but the elevated IGF-II levels were found in only 13 patients. Serum IGF-I levels were low in all patients with NICTH. In the 13 patients without big IGF-II, serum IGF-II levels were lower than those in the patients with big IGF-II, and serum IGF-I levels were also low. Serum IGF-II/IGF-I ratios in the patients with big IGF-II were elevated and greater than those in the patients without big IGF-II (35.0+/-2.2 vs. 11.5+/-2.4). The present data indicate that IGF-II-producing tumors are not rare in NICTH, and serum big IGF-II and IGF-II/IGF-I ratio are useful for screening patients with IGF-II-producing NICTH.