Androgen Level in the Sheep Fetus During Gestation

The androgen content of amniotic fluid, plasma, and gonads from 107 fetal lambs was determined by radioimmunoassay in an attempt to understand the ontogeny of gonadal function. Testosterone (T) was too low to be reliably measured in the amniotic fluid from fetuses of either sex. Ovaries were without T activity at an ofy the stages of gestation studied. Testicular T-5α-dihydrotestosterone (T-DHT) concentration steadily decreased from 1.4 ± 0.2 to 0.08 ± 0.01 μg T-DHT/g testis during the last 80 days of gestation. This was due to both increasing gonadal size as well as a decline in the absolute amount of T-DHT/testis. T was detected in the plasma of fetuses of both sexes. In females, levels rose steadily from 112 ± 20 to 459 ± 223 pg/ml during the last 80 days of fetal development. The pattern in the male was different in that plasma T at 70 days of gestation was 658 ± 145 pg/ml; then fell to 279 ± 51 pg/ml at about 100 days of gestation. Plasma T then rose to 866 ± 141 pg/ml near term. It is suggested that nongonadal testosterone production increases during fetal life and that T secretion by the fetal testis may contribute steadily less to the plasma pool of T as gestation proceeds.