Hormone Replacement Therapy
©2006 Publications International, Ltd.
Hormone replacement therapy (HRT) is one of the most controversial approaches to the management of menopausal symptoms. HRT literally replaces the hormones that a woman's body no longer produces. There are two primary types of HRT: estrogen replacement therapy (ERT) and combination estrogen/progesterone therapy. Other hormones less commonly used in HRT include androgens, specifically testosterone, and dehidroepiandrosterone (DHEA).
Estrogen is primarily produced in a woman's ovaries. The ovaries produce little estrogen during childhood, but at puberty, estrogen production increases, making girls develop breasts and wider hips and building the uterine lining each month in preparation for pregnancy. In the central nervous system, estrogen and its companion hormone, progesterone, help to regulate mood and sleep-wake cycles. During menopause, the ovaries begin to shut down; they no longer produce eggs and stop producing estrogen and progesterone.
Some doctors think that menopause is a "failure of the ovaries" and that estrogen should be given indefinitely to almost every woman going through menopause. But most doctors think that HRT should be used only for a short period of time to alleviate severe symptoms of menopause.
Doctors have learned quite a bit since HRT was first introduced. In the l940s, scientists discovered how to make estrogen that could be taken in a pill. The first orally active estrogen was made from pregnant mares' urine, hence the familiar brand name, Premarin. Premarin and other forms of estrogen became very popular in the l950s. In the 1960s, reports appeared that women taking estrogen supplements had an increased risk of endometrial (uterine) cancer. Further research revealed that as long as estrogen was balanced with a second hormone, progesterone or a synthetic "progestin'" the combination -- which is also used in oral contraceptives -- did not cause endometrial cancer.
By the 1980s, combination estrogen/progestin therapy was widely used to manage menopausal symptoms in women who had a uterus, but it was not usually used to treat women who had hysterectomies, as they do not need protection from endometrial cancer. At the time, many thought that the combination therapy might protect women against heart disease and Alzheimer's disease as well, but this has never been proven.
In the 1990s, the federal government funded clinical trials to evaluate the safety of HRT. The Women's Health Initiative conducted two studies: the estrogen-alone study of women who had hysterectomies and the combination estrogen/progestin study of women with a uterus. Conclusions from both studies showed that HRT increases women's risk of stroke and blood clots. The estrogen-alone study indicated no increased risk for heart attack or colorectal cancer and a decreased risk of fractures, but effects on breast cancer were uncertain.
However, the combination estrogen/progestin study indicated an increased risk of heart attack and breast cancer and a decreased risk of colorectal cancer and fractures. As a result of the studies, the Food and Drug Administration (FDA) recommends that women who use HRT take the lowest effective dose for the shortest amount of time possible, that health care providers consider prescribing topical products to address vaginal symptoms, and that non-estrogen medications be considered first to treat women at risk for osteoporosis.
Why would a woman use HRT? There are several benefits. Estrogen helps to preserve bone mass and prevent fractures, alleviates thinning of the vaginal wall and bladder, and effectively treats hot flashes. Many women also feel better on HRT; they sleep more soundly, have more energy, and feel less fatigue and irritability. And many find that their skin seems moister and less prone to wrinkling.
Recently, products advertising that they are "natural" or "bioidentical" have been gaining popularity. The term "natural" is primarily a marketing term and is commonly used to describe herbal and over-the-counter nutritional supplements aimed at treating menopausal symptoms. "Bioidentical" hormones are chemically identical to those the human body produces. No large-scale, long-term clinical trials have been conducted to evaluate the safety of these products.
When taking estrogen, taking progesterone protects against endometrial cancer. But estrogen can also be combined with another hormone, testosterone. Although usually thought of as a male hormone, testosterone is, in fact, produced in small amounts in women's ovaries. Some women notice a decrease in libido and general well-being after menopause (particularly surgical menopause) but find that taking testosterone supplements improves their sex drive. However, side effects include facial hair, thinning scalp hair, acne, and deepening of the voice. Furthermore, most of the products on the market are for males and use in women is "off-label." There have been no long-term safety studies of testosterone use in women.
Another hormone, DHEA, which is normally made in the adrenal glands, is available in over-the-counter supplements, and some studies indicate it can improve libido and well-being. Since the FDA has classed it as a dietary supplement and it is available over the counter, DHEA is not as tightly regulated as are prescription pharmaceuticals, and as a result, products may vary in potency. No long-term safety studies have been done.
Side effects of HRT are common; many women experience vaginal spotting and bleeding, fluid retention, and breast tenderness. Many blame midlife weight gain on HRT, although aging and slowing metabolic rate are probably the culprits.
The brand name products mentioned in this publication are trademarks or service marks of their respective companies. The mention of any product in this publication does not constitute an endorsement by the respective proprietors of Publications International, Ltd. or HowStuffWorks.com, nor does it constitute an endorsement by any of these companies that their products should be used in the manner described in this publication.