Steroid Levels in the Human Fetus: Cortisol and Cortisone

Abstract

Although much information is available regarding the enzyme systems present in the fetus, there are no direct studies of the levels of unconjugated corticoids in serum and tissues. To determine how the corticoid profile during gestation compares with that of the neonate, cord blood and fetal tissues were obtained at hysterotomy and analyzed by competitive binding to corticosteroid binding globulin (CBG) before and after fractionation using Sephadex LH-20 column chromatography. Identity of the steroids measured was confirmed by comparative binding to dog, human, monkey and chicken CBG and also by constancy of SA after multiple chromatographies. Levels (mean ± se) of cortisol (F) and cortisone (E) for fetuses from 8–18 weeks' gestation were: serum—F 7.3 ± 1.3 ng/ml, E 32.5 ± 8.6 ng/ml; adrenal—F 207 ± 54 ng/g, E 116 ± 25 ng/g. Serum levels for babies delivered by Caesarean section at 36–41 weeks without labor were F 21.7 ± 4.5 ng/ml, and E 89.4 ± 8.6 ng/ml. These levels were lower than those found in the sera of babies born after spontaneous labor: F 70.0 ± 4.5 ng/ml, and E 112 ± 5 ng/ml. The F/E ratio which remains about 0.2 throughout gestation thus alters with labor to about 0.6. These results suggest that the fetal adrenal secretes cortisol, and, to a much lesser extent, cortisone from the first trimester, that the levels triple late in pregnancy and that the cortisol level undergoes a further abrupt rise in association with labor.