Hormone Replacement Therapy (HRT)--the medicinal use of hormones to counter the short- and long-term effects of menopause--is a complex and contentious issue. In this three-part series, we'll examine the medical reasoning behind HRT and the controversies surrounding it. Part 2 will discuss the short- and long-term risks and benefits associated with HRT. Part 3 will review the various forms of HRT as well as some of the nonhormonal alternatives.

Menopause and hormone production

It's common knowledge that a woman's ovaries play a key reproductive role. Every month, during her fertile years, a woman ovulates--releases an egg from one or the other ovary for potential fertilization. If the egg is not fertilized, she menstruates, and the monthly cycle repeats.

What many people do not realize, however, is that eggs are not manufactured by the ovaries, only nurtured and matured there. In fact, a woman is born with all the eggs she will ever have, and by the time she reaches her mid to late 40s, on average, her store of viable eggs is fast approaching zero. When no viable eggs remain, ovulation is no longer possible, and menstruation ceases.

The ovaries are the main source of the most important female hormones--estrogen and progesterone. In fact, the process of maturing and releasing eggs regulates production of these hormones. As a woman's supply of viable eggs dwindles, ovulation and the production of estrogen and progesterone can become highly erratic, and by the time she reaches menopause (her final menstrual period), hormone production is dramatically reduced.

The clinical rationale for HRT

Estrogen and progesterone are principally recognized for their role in the female reproductive cycle, but both play important roles elsewhere in the body. Estrogen and progesterone receptors (sites where these hormones "plug in" to do their job) are widely distributed, found in the skin, bone, arteries, heart, liver, brain, intestine, bladder, and nervous system. Progesterone receptors are thought to be just as widely distributed.

Given the role these hormones play in so many parts and so many systems of the body, it's easy to see how a disturbance or reduction in their supply might result in functional abnormalities. And indeed, such are the many "symptoms" of menopause--hot flashes, mood swings, and a thinning of vaginal tissues, to name but a few.

Of greater medical concern, however, are the potential long-term effects of low sex-hormone levels, especially low estrogen. These consequences include osteoporosis (loss of bone mass resulting in bone weakness), atherosclerosis (accumulation of fat-like plaque on the inner walls of the arteries that can reduce or shut off the flow of blood), myocardial infarction (heart attack), and hypertension (high blood pressure).

By one logic, if something is missing, you replace it. Hormone replacement therapy is a means of supplementing what's produced in the body--in this case with additional estrogen and progesterone. And there's no question that estrogen and progesterone "replacement" can reverse or prevent many of the so-called symptoms of menopause. Estrogen therapy, in particular, is also credited with extending the lives of post-menopausal women, through the prevention of osteoporosis and many of the other long-term effects of diminished estrogen production. However, the extent to which HRT confers specific benefits in preventing heart disease is controversial, especially in light of some of the risks involved in long-term HRT. Also controversial are the extent to which HRT has been embraced by the medical community and the resulting notion of menopause as a disease (what some have referred to as the "medicalization" of menopause).

The controversy--not just a case of medical semantics

No one seriously questions the therapeutic value of HRT in treating many of the effects of fluctuating and flagging hormone levels in and around the time of menopause. Likewise, the effect of estrogen in preventing bone disease is well established. But in recent years, a growing number of physician-authors have questioned the use of such terms as 'symptoms' to describe these effects, arguing that menopause is not a disease but a natural transition, hard-wired into woman's biology for good reasons.

Critics of HRT argue that the medicalization of menopause has overemphasized the "symptoms" and their treatment, to the extent that many women are terrorized by the prospect of menopause and many women are encouraged toward HRT when they don't really need it. The feminist critique of current medical practice goes further still, to say that many women are being robbed of the experience of menopause, which is not so grim as popular mythology would suggest. Menopause, they say, can be a time of tremendous personal revelation and growth.

The big issues

Beyond the cultural issues surrounding our view of menopause, estrogen therapy does have several known risks. For example, it's known to increase the risk of cancer of the endometrium (the lining of the uterus). That's why in women with an intact uterus HRT usually includes a progestin, a synthetic progesterone. Why? Progestin is protective against endometrial cancer and neutralizes the risk associated with estrogen-only therapy.

A number of experts also believe that HRT increases the risk of breast cancer; others disagree. HRT can also precipitate liver problems (rarely), gall bladder disease (usually in women with specific risk factors for gall bladder disease), high blood pressure, and fibroids (noncancerous but tumor-like growths in the uterine lining). In addition there are potential "nuisance effects" such as nausea, headache, weight gain, fluid retention, breast tenderness, breakthrough bleeding, and the return of monthly periods--though none of these effects is in any way certain to occur in any given woman.

The question is: Are the proven benefits of HRT worth the risks? The answer is: For some women, yes. Who would deny the value of short-term estrogen therapy for the woman whose days are punctuated with many unpredictable and thoroughly debilitating hot flashes? Or for the woman who loses quality sleep because of drenching night sweats? On the other hand, it's probably fair to say that some women wind up on HRT before they ever experience the first menopausal "symptom," or that some of these issues, depending on their severity, might be manageable with alternative therapies or other strategies.

Where does this leave us?

There is no real "party line" anymore when it comes to HRT. Its clinical value is indisputable, and the increased risk of serious adverse effects may be negligible for some women. The decision to employ HRT is one each woman must make for herself in consultation with her physician. If she's lucky, or diligent, that physician will be well-versed in the management of menopause and able to help her assess the risks and benefits.