DECREASED GROWTH HORMONE (GH) BINDING TO IM-9 CELLS IN CHILDREN WITH BIOLOGICALLY INACTIVE GH SYNDROME (BI)

Abstract

We measured the ratio of radioreceptor assayable (RRA) to radioimunoassayable (RIA) GH in: a/ Fifteen normal stature children and young adults (controls), b/ Seven poorly growing children (neurosecretory; NS) who had normal GH RIA responses to stimulation but deficient 24-hour integrated concentration of GH (IC-GH). c/ Six poorly growing children (bioinactive; BI) who had normal GH secretion both to stimulation and IC-GH. The BI group was 9.1±3 (mean ± SD) years of age, bone age 6.1±2.7 years, IC-GH 6±2.4 ng/ml (normal 3.2-12). On GH therapy the growth rate of BI patients increased from 3.2±0.5 cm/yr to 8.8±1.9 cm/year.RRA was a modification of a previously reported RRA using IM-9 lymphocytes. The RRA/RIA was 1.3±0.4 in controls, 1.5±0.7 in NS and 0.6±0.6 in BI patients. The difference in RRA/RIA between BI patients and controls was significant (P<0.005).We conclude that 1/ The circulating GH of NS patients has a normal binding affinity to IM-9 cells. 2/ Decreased binding to IM-9 cells may be a clinically useful diagnostic test for BI.