Measurement of Insulin-Like Growth Factor I (IGF-I) in Normal Adults, Patients with Liver Cirrhosis and Acromegaly: Experience with a New Competitive Enzyme Immunoassay

Summary

A competitive enzyme immunoassay for the determination of human insulin-like growth factor I in microtiter plates was established. Using a polyclonal antiserum raised in rabbits against hIGF-I ovalbumin conjugate the assay system was able to detect IGF-I at a range of 12 — 800 pg/well with a sensitivity of 10pg/well. It showed a low (<0.5%) cross reactivity with hIGF-II. The serum concentrations of IGF-I found by EIA agreed well with those found in a conventional RIA (r = 0.965, p < 0.001). Effects of age and sex on IGF-I levels were studied in 260 normal adults. There was no evidence for sex differences but a steep decline of values from the third to the fourth and from the eigth to the ninth decade, respectively. To asses the diagnostic capability of the IGF-I determination in liver cirrhosis, 71 sera of patients classified according to Child classes (A —C) were measured. Although significantly diminished concentrations were found in class B vs A and in class C vs B, the diagnostic sensitivity in crossectional examinations proved to be low (class A: 0.33, class B: 0.67). Only in the case of extensively destroyed liver parenchym (Child C: 0.94) IGF-I was a good indicator of impaired hepatocellular capacity. In 29 patients with acromegaly serum IGF-I levels were investigated. All patients with active acromegaly showed increased IGF-I levels. In contrast, in inactive or weakly active acromegaly values were considerably lower. The data suggest, that the EIA is a useful tool for the evaluation of the IGF-I concentrations in disturbances of the growth hormone (GH)/IGF-I axis in adults.

Key words

Insulin-like growth factor I - ElA - Age - Liver cirrhosis - Acromegaly