Preliminary investigations into the endocrine systems of subfertile cattle: location of a common lesion (rate-limiting step).
Dairy cows with a variety of clinical conditions were investigated in an attempt to identify the cause(s) of subfertility. Sequential or simultaneous injections of 20 micrograms gonadotrophin-releasing hormone (GnRH), 1 mg oestradiol benzoate and 0.06 mg ACTH(1-24) into five clinical cases of ovarian follicular cysts, two cases of poor body condition and one case of lameness and into control cows revealed a failure in the LH positive-feedback response to oestradiol in all eight clinical cases, but in only two out of twelve control cows. Two of the clinical cases and the two non-responding control cows had high or rising initial progesterone concentrations which would explain the absence of response. All cows studied responded similarly to GnRH and ACTH(1-24). It is suggested that hypothalamus-pituitary control of LH release may involve a rate-limiting step (in the oestradiol positive-feedback system) and that lesions at this point result in subfertility in a variety of clinical situations.
Dobson
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Alam
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D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D003366:Cosyntropin; D004958:Estradiol; D005246:Feedback; D005260:Female; D005497:Follicular Cyst / Q000503:physiopathology / Q000662:veterinary; D007247:Infertility, Female / Q000503:physiopathology / Q000662:veterinary*; D007986:Luteinizing Hormone / Q000097:blood; D010906:Pituitary Hormone-Releasing Hormones
D010906:Pituitary Hormone-Releasing Hormones; D003366:Cosyntropin; D004958:Estradiol; D007986:Luteinizing Hormone