Delayed puberty in lambs chronically treated with oestradiol.

摘要: Intact female lambs were chronically treated with low levels of oestradiol by Silastic implant from 20 weeks age. Reproductive cycles initiated in only 33% these (3 9) compared to 80% untreated females (11 14) 45 when the study was terminated. Moreover, 3 oestradiol-treated which began cycles, age at first oestrus delayed (37 +/- 1 vs 34 for controls). Retardation pubertal process not due absence rise circulating LH. At about 32 age, chronic treatment no longer able suppress tonic LH secretion and serum increased intact, lambs. These results indicate that a maturational decrease responsiveness inhibition can be demonstrated intact female, as ovariectomized female. However, suppression prepubertal also delays onset reproductive cycles. This finding raises possibility secretion, presumably form slow pulses, is necessary development or maintenance ovarian function before puberty. In during last part sexual maturation, ability ovary respond high frequency pulses gonadotrophin may delayed.