Vriend J, Bertalanffy F D, Ralcewicz T A
Biol Reprod. 1987 Apr;36(3):719-28. doi: 10.1095/biolreprod36.3.719.
Since melatonin injections administered near the end of the daily photoperiod influence both gonadal and thyroid hormones in the female hamster, the present study was designed to compare the effects of melatonin and hypothyroidism on the reproductive system and to determine whether thyroid status influenced the action of melatonin on the regulation of the hormones of reproduction. The effects of daily melatonin injections were determined in control hamsters, in hamsters rendered hypothyroid with thiourea, and in hypothyroid hamsters receiving thyroxin (T4) hormone replacement. As previously reported, melatonin injections disrupted estrous cyclicity, disrupted the normal pattern of gonadotropin secretion, and resulted in atrophy of the uterus and vagina. These changes coincided with depressed serum and pituitary prolactin (PRL), and depressed levels of estradiol. The effects of melatonin on uterus, vagina, ovary, and on gonadotropin levels were not prevented by T4 replacement, with the exception of a melatonin-induced increase in serum follicle-stimulating hormone (FSH). This suggested that the cessation of estrous cyclicity was not primarily a result of thyroid deficiency. Hypothyroidism, however, like melatonin, resulted in a reduced number of developing and mature follicles and corpora lutea in the ovaries, and in reduced uterine weight. It also produced follicular atresia, reduced the circulating levels of estradiol, and resulted in reduced incidence of estrus smears. T4 replacement, for 2 weeks, prevented the decline in mature follicles and corpora lutea, reduced the extent of follicular atresia, increased circulating levels of estradiol, and increased uterine weight. PRL and luteinizing hormone (LH) data also provided evidence for antagonistic effects of melatonin and T4 in female hamsters. These data raise the question whether melatonin-induced changes in circulating levels of T4 play a role in the seasonal cycles of reproductive competence in the female hamster.
由于在每日光照周期接近尾声时注射褪黑素会影响雌性仓鼠的性腺激素和甲状腺激素，因此本研究旨在比较褪黑素和甲状腺功能减退对生殖系统的影响，并确定甲状腺状态是否会影响褪黑素对生殖激素调节的作用。在对照仓鼠、用硫脲致甲状腺功能减退的仓鼠以及接受甲状腺素（T4）激素替代的甲状腺功能减退仓鼠中，测定了每日注射褪黑素的效果。如先前报道的那样，注射褪黑素会扰乱发情周期，破坏促性腺激素分泌的正常模式，并导致子宫和阴道萎缩。这些变化与血清和垂体催乳素（PRL）降低以及雌二醇水平降低同时出现。除了褪黑素诱导血清促卵泡生成素（FSH）增加外，T4替代并不能阻止褪黑素对子宫、阴道、卵巢以及促性腺激素水平的影响。这表明发情周期的停止并非主要是甲状腺功能不足的结果。然而，甲状腺功能减退与褪黑素一样，会导致卵巢中发育和成熟卵泡以及黄体数量减少，子宫重量减轻。它还会导致卵泡闭锁，降低雌二醇的循环水平，并导致发情涂片发生率降低。持续2周的T4替代可防止成熟卵泡和黄体数量下降，减少卵泡闭锁程度，增加雌二醇的循环水平，并增加子宫重量。PRL和促黄体生成素（LH）的数据也为褪黑素和T4在雌性仓鼠中的拮抗作用提供了证据。这些数据提出了一个问题，即褪黑素诱导的T4循环水平变化是否在雌性仓鼠生殖能力的季节性周期中起作用。
