The aging ovary

During reproductive life, ovarian steroid biosynthesis is gonadotropin depe ndent and occurs in theca and granulosa cells. In the menopausal ovary, the re is atresia of ovarian follicles, with sparing of the androgen-producing theca-interstitial cell component. The aging ovary, therefore, produces sig nificantly reduced amounts of estrogen, with continued, though decreased, a ndrogen production. After menopause, ovarian estradiol biosynthesis is mini mal, with circulating estrogen being derived principally from peripheral ar omatization of ovarian and adrenal androgens. Androgen biosynthesis from th e adrenal gland, in addition to that from the ovary, decreases with age. Al though ovarian androgen production declines with age, there is not an abrup t decrease as is seen with ovarian estrogen levels at the time of menopause . The biological activity of these steroids, either before or after menopau se, depends on the amount of steroid available in the unbound fraction. To this end, sex hormone-binding globulin (SHBG) levels are an important deter minant of hormone action. Not only does the concentration of SHBG influence the biological effect of testosterone and estradiol, but these steroids al so regulate SHBG concentrations.