Freeman M E, LaRochelle F T, Moore R B
Endocrinology. 1976 Sep;99(3):713-9. doi: 10.1210/endo-99-3-713.
This study was designed to describe the effects of thyroid status on the preovulatory surge of LH and to determine the site(s) at which these effects are exerted. The treatment of normal 4-day cycling rats with a hyperthyroid dose of thyroxine (T4, 20 mug/100 g BW/day) for 8 days resulted in surges of LH on proestrus which were depressed to 25% of control levels. In ovariectomized (OV) or ovariectomized-thyroidectomized (OV-Tx) rats maintained on a physiological regimen of T4 (2 mug/100 gBW/day), the amount of estrogen required to induce an LH surge was far greater than that required in OV-TX rats receiving no T4 replacement. These data suggest that T4 attenuates preovulatory surges of LH by acting at the hypothalamic-pituitary axis. However, the pituitary might be eliminated as a site of action since hyerthyroid proestrous rats responded to a challenge of LH-releasing hormone (500 ng) by secreting a quantity of LH equivalent to that in euthyroid animals. Similarly, there was no difference in the quantity of LH released by hyperthyroid and euthyroid proestrous rats in response to electrochemical stimulation (100 muA, 60 sec) of the medial preoptic area of the hypothalamus. On the other hand, hyperthyroid rats secreted significantly less LH in response to stimulation of the arcuate nucleus-median eminence area (ARN-ME) than did controls. Thus, T4, apparently modifies LH release by depressing the response of the ARN.
本研究旨在描述甲状腺状态对促黄体生成素（LH）排卵前激增的影响，并确定这些影响发挥作用的部位。用甲状腺素超生理剂量（T4，20微克/100克体重/天）对正常4天周期的大鼠进行8天治疗，导致动情前期LH激增，降至对照水平的25%。在接受T4生理剂量（2微克/100克体重/天）维持的去卵巢（OV）或去卵巢-甲状腺切除（OV-Tx）大鼠中，诱导LH激增所需的雌激素量远大于未接受T4替代的OV-Tx大鼠。这些数据表明，T4通过作用于下丘脑-垂体轴来减弱LH的排卵前激增。然而，垂体可能被排除为作用部位，因为甲状腺功能亢进的动情前期大鼠对促黄体生成素释放激素（500纳克）的刺激反应是分泌与甲状腺功能正常动物相当量的LH。同样，甲状腺功能亢进和甲状腺功能正常的动情前期大鼠对下丘脑视前内侧区的电化学刺激（100微安，60秒）反应释放的LH量没有差异。另一方面，甲状腺功能亢进的大鼠对弓状核-正中隆起区（ARN-ME）刺激的反应分泌的LH明显少于对照组。因此，T4显然通过抑制ARN的反应来改变LH的释放。
