Delayed puberty in lambs chronically treated with oestradiol

Journal of Reproduction and Fertility
D L FosterS M Yellon

Abstract

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

Citations

Jul 27, 2002·Domestic Animal Endocrinology·Jane E RobinsonVasantha Padmanabhan
Mar 11, 2011·Journal of Toxicology and Environmental Health. Part a·Vidar BergErik Ropstad
May 26, 2006·Molecular and Cellular Endocrinology·Douglas L FosterVasantha Padmanabhan
May 26, 2016·Reproduction : the Official Journal of the Society for the Study of Fertility·Muraly PuttabyatappaVasantha Padmanabhan
Oct 22, 2002·American Journal of Physiology. Endocrinology and Metabolism·Toni R PakPei-San Tsai

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