Episodic Patterns of Prolactin and Thyrotropin Secretion in Rams and Wethers: Influence of Testosterone and Diethylstilbestrol

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Abstract
Rams and wethers were used to define temporal secretory patterns of prolactin (PRL) and thyrotropin (TSH). The influence of exogenous testosterone propionate (TP) and diethyl-stilbestrol (DES) on PRL and TSH in wethers were also studied to determine if the anabolic effects of these agents (TP and DES) could partially be due to stimulation of PRL and/or TSH secretion. Rams and wethers were observed to secrete PRL and TSH in an episodic manner. Secretory episodes appeared to occur at random in all animals. After partitioning of PRL secretory patterns into overall mean concentration, baseline mean concentration, amplitude and frequency of secretory episodes, it was observed that overall and baseline means as well as amplitude of secretory spikes (episodes) were higher (P<.05) in rams sampled in September than in wethers during December. Treatment of wethers with TP (100 mg/day for 3 weeks) increased (P<.05) mean amplitude of PRL secretory spikes and hence overall PRL concentration. Baseline PRL concentration was not significantly influenced by TP. Similarly, treatment of wethers with DES (2 mg/day for 3 weeks) increased (P<.05) baseline, amplitude and overall PRL concentration. Frequency of PRL secretory episodes was not different (P>.05) between any of the treatment groups. No differences (P>.05) were observed in baseline, amplitude, frequency or overall TSH concentrations between rams, wethers and TP treated wethers. Higher (P<.05) baseline and overall TSH concentrations were observed in wethers treated with DES. In view of reported anabolic effects of PRL and the recognized role of thyroid hormones in growth, these results support the suggestion that TP and DES may exert their anabolic actions in part by stimulation of PRL and/or TSH secretion. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.