Immunoreactive IGF-II in serum of healthy subjects and patients with growth hormone disturbances and uraemia.

A radioimmunoassay has been 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 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 to 70 years. 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 less than 0.001) compared to controls. In diabetic patients with uraemia the mean level and 95% confidence limit were 1222 ng/ml and 532-2808 ng/ml, respectively. Thus, significantly increased serum levels of immunoreactive IGF-II have only been found in serum from patients with uraemia. 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.