Serum hormones in response to estradiol and (OR) progesterone in ovariectomized cows after thyroidectomy |
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| Institution: | 1. Department of Pharmacology and Biotechnology, São Paulo State University - UNESP, Botucatu, SP, Brazil;2. Department of Animal Reproduction, University of São Paulo - USP, Pirassununga, SP, Brazil;3. Department of Animal Sciences, University of Florida – UF, Gainesville, FL, USA;4. Faculty of Animal Science and Food Engineering, Department of Veterinary Medicine, University of São Paulo – USP, Pirassununga, SP, Brazil;5. Departament of Animal and Dairy Sciences and Brown Loam Experiment Station, Mississipi State University, Raymond, Mississipi, USA;6. Agrarian Sciences Center, State University of Maranhão Tocantins Region, Imperatriz, MA, Brazil;7. Department of Animal Sciences, São Paulo State University - UNESP, Dracena, SP, Brazil;1. Department of Animal Science, Luiz de Queiroz College of Agriculture (ESALQ/USP), University of São Paulo, Piracicaba, SP, Brazil, 13418-900;2. Department of Animal and Dairy Sciences, University of Wisconsin–Madison, Madison 53706;1. Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, 53706, USA;2. Department of Animal Science, University of São Paulo, Piracicaba, SP, 13418-900, Brazil;3. Department of Animal Sciences, The Ohio State University, Columbus, OH, 43210, USA |
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| Abstract: | To evaluate the effect of gonadal steroid treatment and thyroidectomy on concentrations of gonadotropins and thyroid-stimulating hormone in the bovine, nonlactating Holstein cows were either thyroidectomized and ovariectomized (THYOVEX; n=6) or ovariectomized only (OVEX; n=4), and subsequently treated with no gonadal steroids (control), estradiol-17β (E2), progesterone (P4), or P4+E2 in a 2 × 4 factorial experiment. Averaged across steroid treatments, baseline concentrations of luteinizing hormone (LH; P < .05) and follicle-stimulating hormone (FSH; P <.10) were higher in THYOVEX cows than in OVEX cows. Pulse frequencies and amplitudes of LH and FSH did not differ between THYOVEX and OVEX cows. Secretion of TSH was pulsatile and all concentrations and pulsatile characteristics of TSH were increased (P < .05) in THYOVEX compared to OVEX cows. Treatment with E2 and P4 decreased (P < .05) baseline concentrations and magnitude of LH pulses, whereas P4+E2 increased (P < .01) pulse frequency of LH and FSH. Amplitude of LH and FSH pulses were not affected by treatment with either steroid. Treatment with P4+E2 decreased (P < .05) baseline concentrations of TSH, whereas pulse frequency, and magnitude and amplitude of TSH pulses were not altered by treatment with steroids. Mean concentrations of LH and FSH were similar during 48 hr after termination of E2 and P4+E2 treatments, but concentrations of TSH were higher (P = .06) after P4+E2 than after E2. Secretion of TSH showed a diurnal variation, with the lowest concentrations in the morning and highest in the afternoon. These results indicate that thyroidectomy influenced secretion of gonadotropins in OVEX cows. |
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