SEX-DIFFERENCES IN SERUM HORMONE LEVELS IN UMBILICAL VEIN BLOOD

OBJECTIVE: To determine the serum levels of FSH, LH, PRL, estradiol, progesterone and testosterone in umbilical vein blood in a group of normal neonates. METHOD: Umbilical vein blood was obtained for serum analyses from 52 newborns (25 females and 27 males) in the Maternity of the Hospital Regional Virgen de las Nieves, Granada (Spain) and means were compared with Student's t-test. RESULT: Mean values of prolactin, estradiol and progesterone were similar in both sexes. The levels of gonadotropins in umbilical vein blood found were significantly higher in newborn males than in females (P < 0.001 for LH, P < 0.007 for FSH). Testosterone levels were higher in male neonates than in females (P < 0.004). CONCLUSION: Our data reflect the dynamic state of male fetal endocrinological status in comparison to female fetuses, and strongly suggest that the mechanisms of hormonal regulation differ in the two sexes.