Postnatal ovarian activation has effects in estrogen target tissues in infant girls.
BACKGROUND
Shortly after birth, pituitary gonadotropin secretion transiently activates in both sexes, and this surge is more robust 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.


METHODS
We measured urinary estradiol (E₂) levels in 29 FT and 34 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 < .0001). Urinary E₂ levels in PT girls were positively associated with mammary gland and uterine growth.


CONCLUSIONS
These findings indicate that gonadal steroidogenesis activates during the postnatal gonadotropin surge in girls. In addition, the resulting elevated E₂ levels affect target tissues, suggesting that postnatal pituitary-ovarian activation plays a role in normal female reproductive development.
William Harvey Research Institute, Barts and the London, Queen Mary University of London, London EC1M 6BQ, United Kingdom. l.dunkel@qmul.ac.uk.
Tanja
T
Kuiri-Hänninen
Mikko
M
Haanpää
Ursula
U
Turpeinen
Esa
E
Hämäläinen
Raija
R
Seuri
Erja
E
Tyrväinen
Ulla
U
Sankilampi
Leo
L
Dunkel
D015415:Biomarkers / Q000652:urine; D002657:Child Development; D015331:Cohort Studies; D004958:Estradiol / Q000378:metabolism / Q000652:urine; D005260:Female; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008137:Longitudinal Studies; D008297:Male; D042361:Mammary Glands, Human / Q000378:metabolism / Q000473:pathology; D009092:Mucous Membrane / Q000378:metabolism / Q000473:pathology; D009929:Organ Size; D010053:Ovary / Q000378:metabolism* / Q000473:pathology; D010902:Pituitary Gland / Q000378:metabolism* / Q000473:pathology; D047928:Premature Birth / Q000097:blood / Q000378:metabolism* / Q000473:pathology; D011446:Prospective Studies; D012727:Sex Characteristics; D015854:Up-Regulation; D014599:Uterus / Q000378:metabolism / Q000473:pathology; D014844:Vulva / Q000378:metabolism / Q000473:pathology
D015415:Biomarkers; D012739:Gonadal Steroid Hormones; D004958:Estradiol