The human fetal prolactin and estradiol levels, and their correlationship.

Serum prolactin and estradiol-17 beta levels were determined in umbilical cord sera obtained from 33 preterm, 118 full-term and 11 anencephalic infants and in peripheral sera obtained from 5 neonates. Prolactin levels increased from mid-gestation toward term, and markedly decreased after birth. Those in anencephalic infants (253 +/- 86 ng/ml, mean +/- S.D.) were lower than in full-term infants (324 +/- 119 ng/ml), but the difference was not statistically significant. We also performed thyroid-releasing-hormone (TRH) (50-200 micrograms) test on 5 anencephalic infants, but significant changes of serum prolactin levels were not found. Estradiol-17 beta levels in anencephalic infants were significantly lower than those in full-term infants. There was a significant positive correlation between cord prolactin and estradiol-17 beta levels in full-term infants. These results suggest one of the control factors for human fetal pituitary prolactin secretion is estrogen, and hypothalamic factors are not so important.