DOSE-DEPENDENT INHIBITION OF GROWTH-HORMONE (GH)-RELEASING HORMONE-INDUCED GH RELEASE BY CORTICOTROPIN-RELEASING HORMONE IN PREPUBERTAL CHILDREN

Previous studies have shown that CRH is capable of inhibiting GH relea se in response to GHRH in adult subjects, and this effect appeared to be sex dependent and more pronounced in women than in men. To assess w hether CRH has an inhibitory action on GH release in children also, th e effects of graded doses of CRH on the GHRH-induced GH secretion were studied in three groups of prepubertal children. All subjects underwe nt a GHRH test(1 mu g/kg), followed, on separate occasions, by the com bined administration of GHRH (1 mu g/kg) and CRH (1 mu g/kg, group A, n = 6; 1.5 mu g/kg, group B, n = 6; 2 mu g/kg, group C, n = 7). GH con centrations in response to the single GHRH injection were comparable i n the three groups. The combined administration of GHRH and CRH result ed in serum GH concentrations similar to those obtained in the same su bjects in response to GHRH alone when 1 and 1.5 mu g/kg CRH were given . In contrast, the administration of 2 mu g/kg CRH together with GHRH led to an increase in GH concentrations significantly lower than those after the GHRH injection alone (GH area under the curve, 1022.18 +/- 106.26 vs. 3109.16 +/- 794.29 mu g/L . 24 h; P < 0.05). No differences in the GH response to GHRH alone or to GHRH plus CRH were detected be tween male and female subjects. The results of the present study indic ate that CRH is capable of inhibiting GHRH-induced GH release in child ren. Moreover, the inhibitory effect by CRH appears to be dose depende nt and not sex related.