Serum Chorionic “Growth Hormone-Prolactin” and Serum Pituitary Growth Hormone in Mother and Fetus at Term

Chorionic “growth hormoneprolactin” (CGP) and pituitary growth hormone (HGH) were measured in maternal and fetal blood obtained simultaneousy at term from 29 pregnant women and their fetuses utilizing sensitive radioimmunoassay procedures. The mean concentration of serum CGP in maternal venous blood was 5.6 μg/ml (sem 0.39), whereas in umbilical venous serum the mean concentration was 0.019 μg/ml (sem 0.003), a 300-fold difference. Contrariwise, the mean concentration of serum HGH in maternal serum was 5.0 mμg/ml (sem 0.52) and in umbilical venous serum the level was 33.5 mμg/ml (sem 4.6). The ratio of serum CGP/HGH in maternal venous serum was 1076 in contrast to 0.57 in umbilical venous serum. These findings strongly suggest that CGP is secreted by the syncytiotrophoblast almost exclusively in a unidirectional manner into the maternal circulation. Further, it is unlikely that an appreciable exchange of HGH occurs between the maternal and fetal circulations. The data support the view that the growth hormone-like metabolic changes observed in pregnancy are attributable to the effects of CGP and are consistent with the hypothesis that CGP is an important metabolic hormone of pregnancy exertingits actions on the mother and possibly the placenta, but only indirectly on the fetus.