Cord serum growth hormone in the human fetus. Sex difference and a negative correlation with birth weight.

Cord venous growth hormone (GH) were measured by radioimmunoassay in 88 infants and 11 anencephalic infants. The mean GH levels decreased gradually from midgestation, preterm to term fetus. There was a significant (p less than 0.01) sex difference in the GH level of term fetuses. Anencephalic infants had low GH levels. There was a significant (p less than 0.01) negative correlation between the cord GH level and birth weight in the normal infant. These data suggest that there is a sex difference for fetal GH secretion and that GH is not so important for fetal growth, but the hypothalamus plays an essential role in the regulation of fetal GH secretion.