Gopinath R, Kitts W D
Growth. 1984 Winter;48(4):515-26.
The effect of estrogenic anabolic compounds on plasma thyroid hormone concentrations was investigated in growing beef steers. Sixteen Hereford beef steers, weighing approximately 380 kg, were randomly placed into four groups and assigned to one of the following treatments: 36 mg implant of Zeranol, 36 mg implant of diethylstilbestrol (DES), one implant of Synovex-S and an unimplanted control. Total thyroxine (T4) and triiodothyronine (T3) concentrations were analyzed from plasma samples collected at different periods following the implantation using a solid phase radioimmunoassay. Free thyroxine concentration was estimated indirectly as free thyroxine assessment (FTA) from total T4 concentration and the binding capacity of thyroxine binding globulin (TBG-RDA). Overall mean plasma T4 concentration was higher in steers implanted with Synovex-S (23%, P less than 0.05) and DES (18%, P = 0.08) than the controls. When compared to controls, a slight increase (2.2%, P greater than 0.05) was observed in steers implanted with zeranol. The TBG-RDA values were lower (P less than 0.05) and the FTA values were higher (P less than 0.05) in steers implanted with estrogenic anabolic compounds than the controls. The FTA values were significantly increased by Synovex-S (57%, P less than 0.05) and were found to be non-significantly increased by DES (37%) and zeranol (30%) when compared to the control values. Mean plasma T3 concentration was not affected (P greater than 0.05) by DES, Synovex-S or zeranol implantation. These data indicate increased plasma total and free T4 concentration in steers due to the implantation of Synovex-S, a non-significant increase due to DES implantation and suggest that it could be one of the mechanisms by which they improve growth and metabolism. Zeranol seems to have a weaker influence on the thyroid gland than Synovex-S or DES. Plasma T3 concentration appears to be unaffected by estrogenic anabolic compounds in steers. While previous investigators have reported a suppression of thyroid gland activity in ruminants treated with androgenic anabolic compounds, the present study indicates a stimulation of thyroid gland activity, as reflected by the elevated T4 concentration, in steers treated with estrogenic anabolic compounds, especially Synovex-S and DES.
在生长中的肉用公牛中研究了雌激素类合成代谢化合物对血浆甲状腺激素浓度的影响。16头体重约380千克的赫里福德肉用公牛被随机分为四组，并给予以下处理之一：植入36毫克玉米赤霉醇、植入36毫克己烯雌酚（DES）、植入一枚复合激素埋植剂Synovex - S以及未植入作为对照。使用固相放射免疫分析法对植入后不同时间段采集的血浆样本中的总甲状腺素（T4）和三碘甲状腺原氨酸（T3）浓度进行分析。游离甲状腺素浓度通过总T4浓度和甲状腺素结合球蛋白结合容量（TBG - RDA）间接估算为游离甲状腺素评估值（FTA）。植入Synovex - S（升高23%，P小于0.05）和DES（升高18%，P = 0.08）的公牛的血浆总T4浓度总体平均值高于对照组。与对照组相比，植入玉米赤霉醇的公牛有轻微升高（2.2%，P大于0.05）。植入雌激素类合成代谢化合物的公牛的TBG - RDA值较低（P小于0.05），FTA值较高（P小于0.05）。与对照值相比，Synovex - S使FTA值显著升高（57%，P小于0.05），DES（37%）和玉米赤霉醇（30%）使其升高但无统计学意义。DES、Synovex - S或玉米赤霉醇植入对血浆T3浓度无影响（P大于0.05）。这些数据表明，由于植入Synovex - S，公牛血浆总T4和游离T4浓度升高，DES植入使其有不显著升高，提示这可能是它们改善生长和代谢的机制之一。玉米赤霉醇对甲状腺的影响似乎比Synovex - S或DES弱。肉用公牛的血浆T3浓度似乎不受雌激素类合成代谢化合物影响。虽然之前的研究者报道用雄激素类合成代谢化合物处理的反刍动物甲状腺活动受到抑制，但本研究表明，在接受雌激素类合成代谢化合物处理的公牛中，尤其是Synovex - S和DES处理的公牛，甲状腺活动受到刺激，这表现为T4浓度升高。
