This article describes the current understanding of androgen, estrogen, and gonadotropin metabolism in menopausal women.
I. Androgens
A. Premenopause
1. Andros t enedione (ADD)
In normal premenopausal women the mean ADD (1500pg/ml) and testosterone (325pg/ml) are similar to the level found in young women. It suggests that one half of the circulating ADD originates from the ovarian secretion and the remainder, from adrenal secretion.
2. Testosterone (T)
The circulating T in the premenopause is derived from ovary, adrenal, or both and peripheral conversion of ADD. The majority of the T circulating after ovariectomy can be accounted for by peripheral conversion of ADD secreted by the adrenal glands. The remainder is the origin of direct adrenal secretion.
B. Postmenopause
1. ADD
In normal postmenopausal the mean ADD concentration(831pg/ml) is one-half the concentration seen in premenopausal women. Menopause is associated with a marked decrease in ovarian ADD secretion The adrenal gland appears to secrete comparable amounts of ADD before and after the menopause.
2. T
The mean concentration (231pg/ml) is minimally lower than the one found in premenopausal women.
The postmenopausal ovary secretes more T than the premenopausal gonad. A proposed mechanism for the increased ovarian T production by postmenopausal ovaries is the stimulation of gonadal cells capable of androgen production by excess endogenous gonadotropins, which in turn are increased because´of reduced estrogen by the ovaries.
H. Estrogens
A. Premenopause
1. Estradiol (E,)
In normal premenopausal women the mean E, concentration is lower than the level found in young women. Most E, is secreted directly by the ovary. The small amount of E, still circulating after ovariec
tomy probably results from peripheral conversion of testosterone and estrone.
2. Estrone (E,)
The concentration of E, in premenopausal women is somewhat lower than in young women.The sources of circulating E, in preinenopause are direct ovarian secretion and peripheral conversion of ADD. In addition, circulating E, can be converted to E,.
B. Postmenopause
1. E,
Once a woman is postmenopausal, E, levels are more marked decreased than in the premenopausal women. The source of circulating E= may result from peripheral conversion of T and E,.
2. E,
The circulating level of E, is higher than that of E. after the menopause. In postmenopausal women, direct ovarian secretion of E, appears to be essentially absent and plasma estrogens (primarily E,) are mainly derived from the peripheral conversion of ADD, which is produced in the adrenal. ADD produced in the adrenal, ovary, or both is secreted into the circulation. It is then aromatized to E, in peripheral tissues, in particular, adipose tissue. The E, formed in these extraglandular -sites is then secreted into plasma to act at other target tissues.
M. Gonadotropins
As women approach the menopause, FSH levels appear to rise out of the normal range while LH levels remain normal. It appears that sporadic, ovulatory menstrual cycles can occur after a series of anovulatory cycles associated with elevated gonadotropin concentrations in the premenopausal woman. The finding of serum gonadotropin concentration in the premenopausal period is thus no assurance that ovulation and possibly conception can not accur during a subsequent menstrual cycle.
In the postmenopausal women, both LH and FSH levels are significantly elevated over the concentrations seen in premenopausal women, with FSH usually being higher than LH.
Increased luteinizing hormone-releasing factor(LRF) activity has been found in the plasma of post-menopausal women. Both increased hypothalamic secretion of LRF and decreased negative feed back by ovarian estrogens at the pituitary-hypothalamic complex are probably responsible for the increase in LH and FSH production.
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