Postnatal ovarian activation has effects in estrogen target tissues in infant girls

Abstract

Context: Shortly after birth, pituitary gonadotropin secretion transiently activates in both sexes, andthis surge ismorerobust in preterm (PT) than in full-term (FT) infants. In boys, the gonadotropin surge is associated with testicular activity and is considered an important part of normal reproductive development. In contrast, gonadal activation and its consequences in infant girls are poorly understood. Objective: Our objective was to evaluate the association of postnatal ovarian activity with simultaneous changes in estrogen target tissues in FT and PT girls. PatientsandMethods:Wemeasured urinary estradiol (E2) levels in 29 FTand34 PT girls using a mass spectrometric method from 1 week (D7) to 6 months of age (M1-M6). To assess the contribution of ovarian E2 on urinary E2 levels, the levels in girls were compared with the levels of boys of similar cohorts (29 FT and 33 PT boys). E2 levels were compared with simultaneous changes in estrogenic target tissues including mammary glands in both sexes and uterus and vulvar epithelium in girls. Results: Median urinary E2 levels increased after D7 in girls, but not in boys. Mammary gland diameter was larger in girls than in boys from M4 in FT (P < .001) and M2 in PT infants (P < .0001). In PT girls, E2 levels increased at term and were then higher than those in FT girls (P