Postnatal Developmental Changes in the Pituitary-Ovarian Axis in Preterm and Term Infant Girls

Abstract

Postnatal pituitary-testicular activation in infant boys is well characterized. However, the ovarian response to pituitary activation in infancy is less well understood. The aim of the study was to compare postnatal developmental changes in the pituitary-ovarian axis in preterm and term infant girls. Sixty-three infant girls, divided into three groups according to gestational age (GA) [i.e. full term (FT; n = 29; GA, 37-42 wk), near term (NT; n = 17; GA, 34-37 wk), and preterm (PT; n = 17; GA, 24-34 wk)] were examined monthly from 1 wk (D7) to 6 months (M1-M6) of age and reexamined at the corrected age of 14 months (cM14). We performed a longitudinal follow-up of urinary FSH and serum anti-Müllerian hormone (AMH) levels and the number of follicles in transabdominal ovarian ultrasonography. The postnatal FSH surge was stronger and more prolonged in NT and PT girls than in FT girls (P ≤ 0.001). Increased folliculogenesis and a rise in AMH levels were observed in all three groups after the FSH surge. In NT and PT girls, follicular development was delayed in comparison with FT girls, and a decrease in high FSH levels around the 40th postmenstrual week was temporally associated with the appearance of antral follicles in ultrasonography and an increase in AMH levels. The postnatal FSH surge results in transient ovarian stimulation in term and preterm girls. A delay in ovarian folliculogenesis shown in ovarian ultrasonography and by low serum AMH levels may provide an explanation for the exaggerated FSH surge in NT and PT girls.