Postnatal ovarian activation has effects in estrogen target tissues in infant girls
Tanja Kuiri-Hänninen1, Mikko Haanpää, Ursula Turpeinen
1William Harvey Research Institute, Barts and the London, Queen Mary University of London, London EC1M 6BQ, United Kingdom. l.dunkel@qmul.ac.uk.
Insights
Postnatal ovarian activity, indicated by rising estradiol (E₂) levels, influences reproductive tissue development in infant girls. This suggests a crucial role for the pituitary-ovarian axis in early female reproductive maturation.
Area of Science:
- Reproductive Endocrinology
- Pediatric Endocrinology
- Neonatal Development
Background:
- Postnatal pituitary gonadotropin secretion is transiently activated in both sexes, more robustly in preterm (PT) infants.
- While testicular activity is linked to this surge in boys, gonadal activation in infant girls remains poorly understood.
Purpose of the Study:
- To evaluate the association between postnatal ovarian activity and estrogen target tissue changes in full-term (FT) and preterm (PT) infant girls.
- To compare estrogen levels and target tissue responses between sexes to understand ovarian contribution.
Main Methods:
- Urinary estradiol (E₂) levels were measured in FT and PT girls (n=29 and 34) from 1 week to 6 months using mass spectrometry.
- E₂ levels in girls were compared with those in FT and PT boys (n=29 and 33).
- E₂ levels were correlated with simultaneous changes in mammary glands, uterus, and vulvar epithelium.
Main Results:
- Median urinary E₂ levels increased after day 7 in girls but not in boys.
- Mammary gland diameter was larger in girls than boys from M2 (PT) and M4 (FT).
- PT girls exhibited higher E₂ levels at term compared to FT girls, positively associated with mammary gland and uterine growth.
Conclusions:
- Gonadal steroidogenesis activates in girls during the postnatal gonadotropin surge.
- Elevated postnatal estradiol (E₂) levels impact estrogen target tissues in infant girls.
- Postnatal pituitary-ovarian activation is integral to normal female reproductive development.
Context:
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.
Patients And 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.
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