Sex-specific sensitivity of the hypothalamic pituitary axis to estradiol benzoate in normal children

Abstract

The influence of i.m. estradiol benz. (EB)(10-15 mcg/kg) on basal plasma E2, LH and FSH and their response to LRH (50 mcg/m2 i. v.) in normal children was studied. In all pubertal (n=10), early (n=15) and late pubertal (n=6) boys the single EB inj. suppressed basal LH and FSH and their response to LRH. Pre- (n=5) and early pubertal (n=6) girls had suppression of basal LH and FSH but in late puberty (n=14) the basal LH rose from 1.2±0.5 to 3.0±1.6 mIU/ml (p < 0.05) whereas FSH remained suppressed. The mean peak response of LH to LRH following EB (single inj.) was increased in all pubertal stages (to 1.7±0.4, 17.0±14.8 & 27.3±23.6 mIU/ml respectively). FSH response was increased only in early and late puberty (to 13.4±6.0 and 10.5±1.8 mIU/ml respectively). Following 4 daily EB inj. basal plasma LH and FSH levels and their response to LRH in boys (n=22) and girls (n=17) were inconsistently variable in all stages. In conclusion EB modulates the hypothalamic pituitary regulation of gonadotropin secretion, particularly the pituitary response to LRH, which was found to differ at various pubertal stages in normal boys and girls. The sex-specific sensitivity to physiological plasma estrogen levels may be of importance in the maturation of the hypothalamic pituitary axis during puberty.