Serum Testosterone Concentrations in Embryonic and Fetal Pigs During Sexual Differentiation

Abstract

Testosterone concentration in serum of the umbilical artery was greater for male than female fetuses at all stages sampled from Day 30 to Day 112 of gestation. For male fetuses testosterone concentrations increased from Day 30 to a maximum on Day 35 and decreased thereafter. The pattern of testosterone concentrations in amniotic fluid mimicked that observed in serum of the umbilical artery. The concentration of testosterone on Days 40 and 50 of gestation was three to four times greater in the umbilical artery than in the umbilical vein. These data indicate that fetal testes are secreting testosterone in vivo during differentiation of the internal and external genitalia. Serum testosterone concentrations are greater during the stage of sexual differentiation than at later stages.