Changes in hypophysio-ovarian endocrinological function of post-menopausal and castrated women.

The serum levels of estradiol, progesterone, LH and FSH were determined by radioimmunoassay in post-menopausal and castrated women and the data obtained at the same periods after menopause and castration were compared. The serum levels of estradiol and progesterone in post-menopausal women within 1 year after menopause were higher than those of castrated women. The result suggested that ovarian function was indeed depressed in the post-menopausal women but was still preserved for 1 to 2 years after menopause. In the post-menopausal women, the levels of serum LH and FSH rose gradually to reach a peak at 1 to 3 years after menopause, when the production of ovarian sex steroid hormones presumably ceased. On the contrary, the serum LH and FSH levels of castrated women began to decrease gradually 4 to 9 years after castration. It is highly suggestive from these findings that a negative feedback mechanism is elicited by ageing.