IMMUNOREACTIVE IGF-II IN SERUM OF HEALTHY-SUBJECTS AND PATIENTS WITH GROWTH-HORMONE DISTURBANCES AND UREMIA

A radioimmunoassay was developed for IGF-II, using Sepharose-coupled antibodies. Porcine insulin, human insulin and human proinsulin showed no cross-reaction, whereas the cross-reaction for IGF-I [insulin-like growth factor II] was 10%. To minimize the influence of the binding protein(s), all serum samples were extracted with acid ethanol before assay. The mean serum level of immunoreactive IGF-II and 95% confidence limit in 46 healthy adults were 587 ng/ml and 354-974 ng/ml, respectively. In contrast to the declining levels of IGF-I with increasing age, no such age-dependent decrease was found for IGF-II levels between 20-70 yr. No difference in IGF-II levels was found between patients with acromegaly and healthy adult controls. In cord serum and serum from adult patients with GH deficiency the levels were significantly lower (P < 0.001) compared to controls. In diabetic patients with uremia the mean level and 95% confidence limit were 1222 ng ml and 532-2808 ng/ml, respectively. Significantly increased serum levels of immunoreactive IGF-II were only found in serum from patients with uremia. Whether this is due to an increased production of IGF-II, or secondary to other factors such as the binding protein(s), will require further investigation.