Thyrotropin secretion before and after ovariectomy in premenopausal women.

Many studies have shown a physiological reduction in thyroid function with age in animals, and less clearly in humans, with an increase in the incidence of age-dependent clinical and subclinical hypothyroidism. Women are more subject to thyroid dysfunction than men. In postmenopausal women the sudden drop in estrogen levels may affect not only pituitary gonadotropins but also other pituitary hormones directly or indirectly involved in reproductive function. The response of thyrotropin to thyrotropin releasing hormone (TRH) has been shown to decrease with age and basal levels of thyrotropin have been found to be reduced in elderly subjects. In the present study we evaluated the response of thyrotropin to TRH before and after ovariectomy in premenopausal women and during estrogen therapy. The response of thyrotropin to TRH after ovariectomy was significantly less than before. Estrogen replacement therapy restored the thyrotropin response to TRH to pre-ovariectomy levels. This significant decrease in the thyrotropin response to TRH observed in surgical postmenopausal women may be explained by lower endogenous estradiol levels.