Differences of hexarelin-induced prolactin and cortisol responses between prepubertal and early pubertal short children and lack of correlation with gonadotropin-releasing hormone-induced gonadotropin response.

Hexarelin (HEX), a synthetic hexapeptide with strong GH-stimulating activity, is known to induce the release of prolactin (PRL) and cortisol (F). The responses of GH and F vary according to age and pubertal development, correlating with serum levels of sex steroids, while the release of PRL does not. We evaluated GH, PRL and F responses to HEX (2 microg/kg i.v.) in 19 children with short stature, 12 prepubertal (Tanner stage I) and 7 early pubertal (stage II), and their correlation with those of FSH and LH to GnRH and with the serum levels of testosterone (T) or estradiol (E2). At baseline, the GH, PRL, F and sex steroid serum levels did not vary in the two groups of patients. HEX induced a strong GH and a slight PRL increase in prepubertal and early pubertal children, with no differences in the extent of the response, while F secretion was not affected in either group; these responses did not correlate with those of the gonadotropins to GnRH nor with basal T or E2.