Hormone replacement therapy (HRT) uses medications to replace the hormones lost during menopause. It may be taken in various forms, including pills, skin patches, vaginal creams, vaginal rings, suppositories or injections. HRT helps relieve symptoms and prevent diseases brought on by a decrease in the level of estrogen and progesterone experienced by women during and after menopause. About six million American women take a combination of estrogen and synthetic progesterone after menopause, according to the National Heart, Lung and Blood Institute.

Hormones are chemical substances that carry important information and instructions from one group of cells to another. The two most important sex hormones are estrogen and testosterone. They contribute to the growth and development of sexual characteristics and reproduction. Both women and men produce estrogen and testosterone. However, women have much higher proportions of estrogen, whereas men have much greater proportions of testosterone.

Estrogen is a major female hormone that appears to offer women a number of important health benefits such as:

• Helps prevent bone loss
  
  
• Helps prevent buildup of plaque in the arteries
  
  
• Keeps the vagina lubricated and supple
  
  
• Keeps the lining of the urethra from thinning, which helps prevent urinary tract infections

During the years just prior to menopause (around age 50), a woman’s ovaries begin to shrink, causing levels of estrogen and progesterone hormones to drop. When estrogen is no longer produced in large amounts by a woman’s ovaries, she will gradually cease to menstruate. However, she also loses the health benefits of estrogen. As a result, she may experience various adverse symptoms (including hot flashes and vaginal dryness) or face increased risks of heart disease, osteoporosis, Alzheimer’s disease and other health risks.

HRT provides benefits to women during and after menopause, including:

• Reduces symptoms associated with menopause. Such symptoms include:
  
• • Hot flashes. This is warmth in the face, neck and chest that can have a range of effects, from mild to severe heat and sweating. It also manifests as night sweats and may cause headaches.
    
    
  • Vaginal dryness. During menopause, vaginal skin may become dry and thin. Sex may become painful, and vaginal itching (pruritus) or burning may occur.
    
    
  • Mood swings.
    
    
• Protects against other diseases. Hormones are known to help prevent certain diseases, such as colon cancer and osteoporosis (a thinning and weakening of the bones). New evidence indicates that HRT may help prevent heart disease in younger women who start treatment shortly after menopause.

Women receiving HRT usually take one of the following:

• Estrogen. Given to women who no longer have a uterus. It is made synthetically from plants and other sources, or made from the urine of pregnant horses.
  
  
• Estrogen with progesterone. Given to women who still have a uterus. The progesterone helps prevent overgrowth of cells (hyperplasia) in the lining of the uterus that can lead to cancer. Progesterone that is made synthetically is called progestin. Another form of progesterone is known as “natural progesterone” or “micronized progesterone.” It is very similar to the natural hormone.

Women usually remain on HRT for anywhere between several months to a few years. For years, physicians regularly prescribed HRT for menopausal and post-menopausal women. However, the Woman’s Health Initiative (sponsored by the National Institutes of Health) – a 15-year study of more than 160,000 post-menopausal women that ended in 2002 – revealed health risks associated with HRT that have made physicians more cautious about prescribing these drugs. Because of this study, the current recommendation is for most menopausal women to not take HRT indefinitely.

Many health risks are now known to be associated with HRT, including blood clots, breast cancer, uterine cancer and others. The Food and Drug Administration (FDA) currently requires manufacturers of estrogen medications to include information about these risks in the labeling and packaging that accompanies the drugs. However, despite the possible risks, it should be emphasized that the likelihood of adverse effects due to HRT is very low in any individual woman.

In addition, recent findings challenge some of the results of the WHI’s 2002 study. According to a new study conducted by researchers from Cornell and Stanford universities, the risk of heart disease may be lowered in women who begin taking HRT before the age of 60 or shortly after onset of menopause. It should be noted, however, that for women who begin HRT after age 60 the same study had mixed results. For the older group of women participants, HRT increased the risk of heart attacks in the first year of treatment, but after two years of treatment HRT began to reduce this risk. The risk of heart disease and stroke varies with age and the health of a woman. Women of menopausal or post-menopausal age must discuss with their physician whether HRT is right for them.

Studies have found that women who use HRT are more likely to:

• Have entered menopause due to surgery (e.g., hysterectomy, oophorectomy) rather than from normal aging
  
  
• Be Caucasian than African-American or Hispanic
  
  
• Have higher levels of education and income
  
  
• Have been counseled about HRT by a physician or other healthcare provider

Women who choose not to undergo HRT can still take several steps to improve their health. These include:

• Have regular checkups with their physician, especially their gynecologist
  
  
• Avoid tobacco products
  
  
• Eat a balanced diet and maintain a healthy body weight
  
  
• Ask a physician about taking calcium or vitamin D supplements to improve bone health
  
  
• Exercise regularly
  
  
• Check blood pressure, cholesterol and blood sugar
  
  
• Schedule breast exams and mammograms
  
  

In addition, new findings link the current national decline in the rate of breast cancer to a decrease in use of HRT by women. A study released in 2006 indicated that the incidence, or new cases, of invasive breast cancer declined in the period from mid-2002 to 2003. The American Cancer Society statistics for 2001 to 2003 indicate that new breast cancer cases leveled off after 20 years of increases. Many factors may contribute to this change, including a major decrease in the use of HRT by women after menopause. However, the cause and effect of such changes are difficult to establish, especially in the short term.