GROWTH-HORMONE (GH)-RELEASING EFFECTS OF SYNTHETIC PEPTIDE GH-RELEASING PEPTIDE-2 AND GH-RELEASING HORMONE(1-29NH(2)) IN CHILDREN WITH GH INSUFFICIENCY AND IDIOPATHIC SHORT STATURE

To investigate how growth hormone (GH)-releasing peptide (GHRP) and GH -releasing hormone (GHRH) interact in patients with short stature, we examined the acute effects of GHRH1-29NH(2), GHRP-2, and the combinati on of GHRH1-29NH(2) and GHRP-2 on GH release in children with GH insuf ficiency ([GHI] group A) and idiopathic short stature ([ISS] group B). Ten children with GHI (aged 11.8 +/- 1.1 years; height, -4.2 +/- 0.5 SDS) and five children with ISS (aged 11.1 +/- 1.2 years; height, -3.2 +/- 0.1 SDS) were studied. Intravenous bolus infusions of GHRH1-29NH( 2) ( 1 mu g/kg), GHRP-2 (1 mu g/kg), and GHRH plus GHRP-2 (each 1 mu g /kg), were administered in a randomized order. Because of the variabil ity of GH responses, results were analyzed by a nonparametric statisti cal method. Patients in group A showed low GH responses to both GHRH1- 29NH(2) and GHRP-2 stimulation: in only three of 10 and one of nine ca ses, respectively, were the peak GH levels above 5.0 mu g/L. GH area u nder the curve (AUG) 90 minutes after GHRP-2 administration was slight ly less than for GHRH1-29NH(2) (179 +/- 150 v 214 +/- 68 mu g/L . min, P = .06). In group B, GH responses to GHRH1-29NH(2) and GHRP-2 were a pproximately of the same magnitude (1,943 +/- 819 v 1,981 +/- 887 mu g /L . min, P = .9). After a combined challenge with GHRH1-29NH(2) and G HRP-2, five of eight children in group A had peak GH concentrations gr eater than 5 mu g/L. GH AUC of the GHRH1-29NH(2) plus GHRP-2 test in g roup A (1,136 +/- 764 mu g/L . min) was significantly greater than GH AUC of the GHRP-2 bolus (P = .02) but was not different from GH AUC of GHRH1-29NH(2) (P = .09). A dramatic response to combined GHRH1-29NH(2 ) and GHRP-2 administration was observed in group B, with peak GH leve ls above 100 mu g/L in four of five children. GH AUC of the GHRH1-29NH (2) and GHRP-2 combined study (7,035 +/- 1,513 mu g/L . min) was signi ficantly greater than the AUC obtained after administration of GHRH1-2 9NH(2) (1,943 +/- 819 mu g/L . min, P = .015) or GHRP-2 (1,982 +/- 887 , P = .014) alone. Thus, although intravenous bolus GHRP-2 was shown t o release GH in children with various forms of short stature, the resp onse is likely to be dependent on the presence of endogenous or exogen ous GHRH. Copyright (C) 1995 by W.B. Saunders Company