Short-term steroid treatment on plasma lh and fsh in castrated rats from birth to puberty

Rats were gonadectomized from birth to either 40 days (females) or 55 days (males) at 5-day intervals and treated for 4 days before sacrifice. Females were treated with estradiol benzoate (Eb) 0.05 µg/100 g b.w.), males with testosterone propionate (Tp) (40 µg/100 g b.w.), and controls with oil. At sacrifice RIA determinations were made of LH and FSH and the weights of uterus, ventral prostate and seminal vesicles recorded. In treated females plasma FSH and LH levels were lowered by treatment mainly from 20 to 35 days, ineffective at 40 days, and by 45 days had partially recovered effectiveness. In treated males at any age plasma FSH was lowered; LH was lowered only at certain ages. Uterine, seminal vesicle and prostate weight increased significantly when animals reached puberty. The female immature gonadotropin system seems to come under gonadal control later than the male’s and its sensitivity changes with maturation.