The effect of intrauterine gonadectomy on fetal and neonatal gonadotrophin secretion in the lamb.

In Exp. 1, sheep fetuses (2 male and 3 female) were gonadectomized between Days 70 and 120 of gestation and their blood LH and FSH levels were compared to those of control animals (4 male, 6 female) at regular times during the first year after birth. In Exp. 2, fetuses (3 male and 5 female) were gonadectomized between Days 50 and 60 of gestation and gonadotrophin levels at Day 90 of gestation were compared to those of control fetuses of the same age. In neither study did the blood LH and FSH levels differ significantly between gonadectomized and intact lambs of either sex in utero or in the first week of life. However, by 2 weeks of age in the males and by 5 weeks of age in the females, gonadotrophin levels were higher in the gonadectomized than in the intact animals and this difference persisted throughout the first year of life. These results imply that fetal and neonatal gonadotrophin levels are suppressed by maternal and placental steroids in the sheep, and not by fetal gonadal hormones.