Serum concentrations of LH and FSH in the healthy newborn

Objective: A sex difference in fetal and neonatal pituitary-gonadal functio n has been well documented. The aim of the following study was to determine sex differences and patterns of basal LH/FSH in the neonatal period. Design: Peripheral venous blood was obtained from 164 healthy full term new borns (91 males, 77 females) for clinically indicated laboratory examinatio ns. Results: In male newborns, LH values were initially low (days 1-5), increas ed between days 6 and 10, and reached maximum levels between days 16 and 20 . Levels of FSH were initially low (days 1-5), increased between days 6 and 10 and reached maximum levels between days 11 and 15. In female newborns, LH levels were generally lower than in newborn boys: levels were initially low, then increased between days 11 and 15 and reached maximum levels at th e end of the newborn period. FSH values were generally higher than in newbo rn boys; there were initially low values with a first peak between days 11 and 15 and a second peak between days 21 and 28. Conclusions: LH values in male newborns were higher and exceeded values in female newborns, whereas FSH values in female newborns exceeded male newbor n values. Male newborns do not exhibit any peaks of LH and FSH activity, wh ereas female: newborns exhibit two FSH peaks during this period.