Postnatal Ovarian Activation Has Effects in Estrogen Target Tissues in Infant Girls

Abstract

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.

Transient Postnatal Gonadal Activation and Growth Velocity in Infancy

“…18 In girls, the subtle E2 surge in infancy is associated with the growth of E2 sensitive tissues, such as the uterus and mammary glands. 16 Taken together, these data indicate that the transient sex steroid surge during minipuberty has biological effects on sensitive target tissues expressing androgen receptor (AR) and estrogen receptors. The current study shows evidence, for the first time, that the growth plates of long bones are also sensitive and influenced by the postnatal sex steroid surge.…”

“…An enzymatic method was used to analyze creatinine concentration before the urine was deep-frozen at −72 °C and stored for the later analyses of T and E2, which were measured by high performance liquid chromatography tandem mass spectrometry as described earlier. 5,16 All results from T and E2 analyses under the detection limit of the assay were set to zero to avoid these results to falsely affect the statistical analyses.…”

“…We have previously shown that the postnatal sex steroid surge has biological effects on hormone-sensitive target tissues. 5,16 In the postnatal period, elevated T levels associate with simultaneous prostate-specific antigen rise from the prostate and growth in penile length. 5 In addition, postnatal urinary androgens are 5 .10…”

Activation of the Hypothalamic-Pituitary-Gonadal Axis in Infancy: Minipuberty

“…At 1 week of age oestradiol levels are low in both sexes, but after this they increase in girls [42] and are then higher than in boys during the following months [42,43]. This is due to endogenous oestrogen production and is associated with a temporary increase in ovarian follicular development [21,42].…”

“…Unlike testosterone levels in boys that show a clear peak at 1-3 months of age and then decrease steadily towards the age of 6 months, oestradiol levels in girls fluctuate (fig. 2) [42], which probably reflects cyclic maturation and atrophy of ovarian follicles. Oestradiol levels decrease during the 2nd year of life [42,45], but higher oestradiol levels in girls than in boys can also be seen with sensitive assays during the prepubertal years [47].…”