A s a woman approaches and then enters midlife she often notices that her body is changing. Her menstrual cycles may become irregular, she can begin to experience hot flashes, mood swings, insomnia, fatigue, vaginal dryness, loss of libido, stress incontinence or other symptoms that signal the onset of menopause -- symptoms that result from a decrease in her sex steroid hormone production. We now know that when sex steroid hormone levels go down, health risks go up. One of the most important decisions a woman is faced with when this happens is whether or not she should consider hormone replacement therapy (HRT).

HRT is the practice of supplementing declining sex steroid hormone levels with prescription hormones. The hormones most commonly used in HRT are estradiol, the body's most potent form of estrogen, progesterone and, more recently, testosterone and DHEA. Studies have shown that HRT not only relieves perimenopausal and menopausal symptoms but also provides considerable long-term health benefits.

Replacement hormones have been scientifically proven to have a protective effect on a woman's heart, bones, brain, colon and teeth, as well as her overall sense of health and well being. And yet, in spite of this substantial and very convincing evidence, only 15% of the women eligible for replacement hormones actually take them. The most common reasons a woman will choose to forgo the benefits of HRT are a lack of knowledge about the associated benefits and risks and a fear of increased risk for breast cancer. However, a 1998 Journal of the American Medical Association (JAMA) study estimated that for 99% of perimenopausal women the benefits of hormone replacement therapy outweighed the risks.

Scientific studies confirm that when a woman's estradiol level goes down, her risk of heart disease goes up dramatically. Heart disease is the number one killer of women over the age of sixty-five. In fact, a woman is ten times more likely to die of a heart attack than she is of breast cancer. Over the course of her lifetime, a woman is twice as likely as a man to have a heart attack and is more at risk for a second attack. Eighty million women are considered to be at risk for heart disease.

Over forty studies have demonstrated that estradiol replacement reduces a postmenopausal woman's risk of heart disease. Estradiol's effect on heart health is multifaceted. To begin with, estradiol increases a woman's HDL level (good cholesterol), and helps to lower her LDL level (bad cholesterol). When HDLs and LDLs are properly balanced, they help prevent plaque formation in the arteries and aid the body in maintaining a healthy heart. A recent study reported that women who took HRT for twelve weeks had a decrease in the viscosity of their blood, which means that their blood was able to pass through veins and arteries more easily.

New scientific investigations are also suggesting that estradiol may not be the only hormone to have a protective influence on a woman's heart. Actually, the sex steroid hormones work together (Hormonal Update Vol 1:1). New studies now suggest that progesterone, testosterone and DHEA each contribute to the maintenance of a healthy heart and cardiovascular system.

Hormone replacement therapy has also been shown to have a positive action in the prevention of osteoporosis. Osteoporosis is a disease that is the result of a depletion of bone cells, making bones more fragile and susceptible to fracture. Nearly half of women over fifty are likely to suffer from an osteoporotic fracture over the course of their lifetime.

Bones are active and are continually renewing themselves. They are constantly breaking down and rebuilding through the action of cells called osteoblasts (bone buildup) and osteoclasts (bone breakdown). However, when a woman enters her forties, her sex steroid hormone production begins to decline and the rate of bone loss can begin to exceed the rate of bone buildup. This loss accelerates dramatically as she goes through menopause and can continue for the rest of her life.

Estradiol replacement decreases the action of the cells that break bone down thus bringing them more into balance with the bone building cells. Testosterone, progesterone and DHEA are now being studied for their roles in strengthening and protecting bones. HRT is associated with a 50 to 80% decrease in spinal fracture and a 25% decrease in other fracture rates when taken for a period of five years.

Science and medicine are learning more about hormone replacement every day. It is becoming clear that estradiol replacement also significantly decreases a woman's risk of Alzheimer's disease. Additional studies show that testosterone, progesterone and DHEA are present and active in brain tissue and may also be contributing factors in the long-term health of the brain. Four million people in the United States have Alzheimer's disease - twice as many women as men.

In the United States, colon cancer is the second leading cause of cancer death, and there is accumulating evidence that estrogen replacement can reduce a woman's risk of colon cancer by as much as 35%. This is a significant benefit. In addition, studies show that women on HRT have increased libido (sex drive), healthier teeth, and they live longer.

Despite the substantial scientific information demonstrating the many benefits of hormone replacement, many women are afraid if they take HRT they will increase their risk for breast cancer. In the past, based on significant epidemiological evidence linking estrogen to breast cancer risk, physicians and oncologists felt that women who either had breast cancer, or were at high risk, should not take HRT. However, a more recent re-evaluation of the clinical trials that address this topic did not find an increased risk of breast cancer recurrence in breast cancer patients who took estrogen. These studies were small and may not have been capable of showing a small increase in risk. So far, there are no definitive clinical studies carried out with women at high risk for breast cancer (such as a strong family history of the disease) on replacement estrogen.

Whether a woman is at high risk for breast cancer or is a breast cancer survivor, the decision to take replacement hormones is one that only she can make. If symptoms of estrogen deficiency severely impact her quality of life, consideration of HRT can be seriously pursued with her physician weighing the benefits against potential risks.

One of most important things to remember when you are considering hormone replacement is that every woman's needs are uniquely her own. Hormone supplementation that is appropriate for one woman might not be necessary for another. Before you start adding hormones to your system, it is important to find out what your body needs. Testing your hormone levels is an effective tool for helping decide whether or not to begin HRT because it targets exactly what's right for you.