Effects of Acute Intravenous Injection of Two Growth Hormone-Releasing Hormones (GHRH 1–40 and 1–29) on Serum Growth Hormone and Other Pituitary Hormones in Short Children with Pulsatile Growth Hormone Secretion

Abstract

We administered two different growth hormone-releasing hormones (GHRH) to 20 short, prepubertal children who had spontaneous secretion of growth hormone (GH), assessed from 24-hour GH secretion profiles (72 sampling periods of 20 min). We compared one i.v. injection of 1 µg/kg of GHRH 1–40 with that of GHRH 1–29 regarding serum concentrations of GH, prolactin, luteinizing hormone, follicle-stimulating hormone and IGF-I. The children were allocated to two groups without statistical randomization. Both groups were given both peptides, with at least 1 week in between. The first group started with GHRH 1–40, the other with GHRH 1–29. The peptides both induced an increased serum concentration of GH of the same magnitude: mean maximal peak of 89 ± 12 mU/1 after GHRH 1–40 and 94 ± 10 mU/1 after GHRH 1–29 (n.s.). The mean difference in maximum serum GH concentration in each child after injection was 52 ± 9 mU/1, range 1–153 mU/1. GHRH 1–29 also induced a short-term, small increase in the concentrations of prolactin (p < 0.05), luteinizing hormone (p < 0.01) and follicle-stimulating hormone (p < 0.05). We conclude that the shorter sequence GHRH 1–29, when given in a dose of 1 µg/kg, gives a rise in serum concentration of GH similar to that after the native form GHRH 1–40.