Evidence is accumulating that just as for men, testosterone is important for maintaining lean muscle mass, assertiveness, and bone density. It is also important for warding off depression, increasing libido, and maintaining the health and sensitivity of the vaginal tissues. The difference is that women only need about a tenth of the circulating testosterone as do men. Where is testosterone produced in women and how is it replaced?
Approximately 30 percent of a woman's testosterone is produced in the ovaries; the other 70 percent is derived from the transformation of adrenal androgen precursors such as DHEA and androstenedione, both of which decline inexorably with age. So, as a woman ages, she will have a decline in her testosterone level.
It is not a precipitous decline as with estradiol at menopause, but is more gradual reflecting the DHEA decline that begins in young adulthood. Yet is profound: women, on average, experience a 50% drop in testosterone level between age 20 and 50--before menopause occurs. Interestingly, the ovarian production of testosterone decreases with age and menopause as well, but less so than the adrenal precursor source. After menopause, therefore, the percentage of total circulating testosterone produced by the ovary rises to more than 50%.
This fact is important when we consider the idea - promulgated by many gynecologic surgeons - that the postmenopausal ovary is a useless organ and can be lopped out during a hysterectomy "because it no longer serves any purpose and is a cancer risk." This practice leaves a woman with an abrupt drop in her testosterone production that she feels acutely, and it probably accounts for the often observed drop off in libido and sense of well being, as well as the weight gain that many women experience after having their ovaries removed as part of a total hysterectomy. These women often say, "I just don't feel the same as I used to," even when they are on adequate estrogen replacement therapy.
We check testosterone levels - here, as with men, the free testosterone level is most important, and in a woman with intact ovaries, restoring DHEAS to youthful levels often will adequately restore the testosterone levels. If not, we will then add bioidentical testosterone to a woman's ERT cream which will always bring it right into the desired range. In a woman who has had her ovaries surgically removed, it is usually necessary to start directly with bioidentical testosterone replacement.
The importance of replacing testosterone in these women is underscored by the fact that even with ERT, they often will continue to be osteoporotic. Most physicians confronted with this situation will add Fosamax or increase the estrogen dose to the point of side effects. But a number of recent studies have shown a normalization of bone density in these patients with the addition of testosterone. This is another proof of the principle that when one replaces all the hormones that decline with age, many of the diseases of aging can be avoided.