The Response of Pituitary Gonadotropes to a Constant Infusion of Luteinizing Hormone-Releasing Hormone (LHRH) in Normal Prepubertal and Pubertal Children and in Children with Abnormalities of Sexual Development

Abstract

The pattern of LHRH-evoked release of LH and FSH by pituitary gonadotrophs and the concomitant gonadal steroid secretion were studied in 28 pubertal and 16 prepubertal children. LHRH was administered at doses of 100 μg and 10 μg by a constant-infusion pump over 3 hours following a 2-hour control period. Gonadotropin concentrations were measured at 15-minute intervals. Mean LH concentrations rose from 2.0 ± 0.4 (SE) mIU/ml (IRP-2-hMG) to 6.2 ± 0.9 (P < .001) in normal prepubertal and from 5.8 ± 0.9 to 28.0 ± 3.6 (P < .001) in normal pubertal children. The peak rise of LH, the mean level attained during the LHRH infusion, and the area under the time-response curve were greater (P < .001) in pubertal than prepubertal children. The serum LH rise had two components in pubertal children in contrast to a single-phased increase in prepubertal children. Pulsatile release of LH was demonstrated during the basal period in pubertal children and during the LHRH infusion in both groups. FSH release was greater in girls than boys at both stages of pubertal development. A 10 μg LHRH infusion released less LH than did 100 μg in the pubertal children, but more than in prepubertal children. In pubertal boys, plasma testosterone rose (P < .001) from 222 ± 45 ng/dl in the control period to 301 ± 59 following 100 μg LHRH. There was no change in plasma testosterone in the prepubertal boys after 100 μg LHRH or in the pubertal boys following 10 μg LHRH. Plasma estradiol did not rise in girls of either maturity group. In children with hypogonadotropic hypogonadism and structural abnormalities of the hypothalamic-pituitary region, there was no LHRH-evoked gonadotropin release. In 2 agonadal girls, the secretion of LH and FSH was greatly exaggerated. The 3-hour LHRH infusion evoked a maturityrelated pituitary LH release and a sex-specific FSH release; a 2-phased pattern of LH secretion was present in pubertal but not in prepubertal children; pulsatile LH release was evoked by the LHRH infusion in prepubertal children.