Treatment effects of intranasal growth hormone releasing peptide-2 in children with short stature

Abstract

Growth hormone-releasing peptide (GHRP)-2 is a synthetic six amino acid peptide that is a potent GH secretagogue. Although it shares no structural homology with GH-releasing hormone, in clinical studies its actions on the pituitary release of GH are similar. It is effective when administered orally and intranasally. For children with GH deficiency, such noninvasive treatments are most desirable and in need of development. Fifteen children with short stature participated in this study. All of the children had a height < 2 S.D. below mean for age, poor height velocity, delayed bone age, and low serum concentrations of IGF-1. These children had been tested with standard GH secretagogues, e.g. arginine, insulin, and L-dopa. Fifty percent of the children were GH deficient, the remainder had idiopathic short stature. The children received testing with GHRH and GHRP-2 as an acute i.v. bolus of 1 microgram/kg; all children in this study demonstrated a GH response > 20 micrograms/l. Each child in this study also demonstrated a GH response > 10 micrograms/l in response to intranasal GHRP-2, in the dose range of 5-20 micrograms/kg. The children were administered intranasal GHRP-2, 5-15 micrograms/kg, twice a day for 3 months, then three times a day. Fifteen children participated in the study for 6 months; six of the children have participated for 18-24 months. Height velocity, serum IGF-1, IGF-binding protein 3 (IGFBP-3) and GH-binding protein (GHBP) concentrations, and GH responses to GHRP-2 by i.v. bolus and intranasal spray were examined during treatment. Height velocity increased from 3.7 +/- 0.2 cm/year to 6.1 +/- 0.3 cm/year at 6 months, 6.0 +/- 0.4 cm/year at 18-24 months. There were no significant changes in IGF-1 or IGF-PB3 concentrations, or in acute GH responses to i.v. or intranasal GHRP-2. GHBP concentrations rose significantly, from 439 +/- 63 pmol/l to 688 +/- 48 pmol/l. In this study, intranasal GHRP-2 administration was well tolerated, and produced a modest but significant increase in growth velocity.