Your body's ability to respond and function normally depends on the coordinated responses of various organ systems.

The organ systems most affected by aging are:

• cardiovascular system: heart and blood vessels

• genitourinary system: kidneys, bladder, and genitals (the sexual organs, which include the outer labia, vagina, uterus, tubes, and ovaries)

• musculoskeletal system: bones, muscles, joints

• the breasts, including nipples and tissue support

• skin and connective tissues beneath the skin.

To function properly, these organ systems depend on:

• a good blood supply to carry oxygen, nutrients, and hormones to tissues of the body

• a healthy nervous system, which ensures an alert mind, good sight and hearing, and efficient response to other bodily needs such as respiration (breathing) and digestion.

Your good health and well-being, particularly when you are over 45 years old, depend largely on whether you have in the past gotten adequate sleep and exercise, eaten nutritious foods, and avoided excessive dependency on nonprescribed drugs, alcohol, and tobacco.

The Role of Sex Hormones

Human sexuality is a coordinated response of both the nervous system and circulatory system (the network through which blood is supplied to the organs). Sexual response also depends on a balance of hormones controlled by the pituitary gland located at the base of the brain.

The follicle-stimulating hormone (FSH) and the luteinizing hormone (LH), which are produced by the pituitary gland, stimulate a woman's ovaries to produce estrogen and progesterone every month.

During childhood and adolescence these hormones are responsible for:

• growth of the genitals and breasts

• the cyclic release of the egg by the ovary (ovulation)

• the cyclic preparation of the lining of the uterus for pregnancy and support of the developing baby

• the menstrual flow of 4 to 5 days and restarting the cycle

• secondary sexual characteristics such as pitch of voice, skin tone, and breast fullness.

Decrease in Female Hormones

Women in their middle to late 40s begin to have irregular, scant, or heavy periods. These changing periods are a symptom of nearing the end of ovarian function and menstruation. Other symptoms may include mild sleeplessness, nervousness, hot flushes, and irritation. Based on these symptoms and an occasional missed period, your doctor may want you to have a simple lab test to check the level of estrogen in your body. The test will tell you and your doctor if you are menopausal.

Menopause is diagnosed when you have not had a period for 6 months. Most women go through menopause between ages 45 and 60.

You and your doctor will need to discuss whether you could benefit from taking estrogen to replace the estrogen that you will lose after menopause, when your ovaries stop functioning. Taking supplemental estrogen is called estrogen replacement therapy (ERT). For women who still have their uterus, progesterone is often added to the estrogen program because it reduces risk of cancer of the uterus, a major concern with ERT in the past. Treatment with both estrogen and progesterone is called hormone replacement therapy (HRT).

Benefits of Estrogen Replacement Therapy

Osteoporosis: Estrogen replacement therapy is the best means of prevention and treatment for osteoporosis. Osteoporosis is a skeletal disorder that reduces bone density, making a woman prone to fractures. The disease accelerates during the early years of menopause with 50% of the loss occurring in the first 8 to 10 years. Untreated, osteoporosis accounts for 80% of all hip fractures. Lack of exercise, family history of the disease, slender body frame, alcoholism, too little calcium in the diet, and cigarette smoking increase the risk.

Coronary Heart Disease: The heart attack rate in the U.S. is 1.2 in 1,000 among women under 40. This number increases to 22.4 in 1,000 for women aged 50 to 60. Recent articles in the medical literature suggest that estrogen reduces the incidence of heart disease in women who are at risk by as much as 50% to 70%. Women at risk include those with angina and hypertension and women who are obese and who smoke heavily.

Researchers feel that there may be a direct link between loss of estrogen and production of cholesterol, leading to coronary heart disease. Studies have shown that ERT use in menopausal women produces a more favorable cholesterol pattern. It increases the good cholesterol while lowering the bad kind.

Psychological Problems: ERT may relieve menopause-related mood swings, insomnia, and depression and thus may improve your sense of self-worth.

Symptoms Linked with Menopause: ERT relieves these symptoms associated with menopause:

• Hot flushes or flashes and night sweats. Without ERT, you may have brief episodes of intense heat and sweating that last 2 to 3 years after menopause or for as long as 5 to 10 years for a few women.

• Vaginal dryness and narrowing that cause pain with intercourse. Less estrogen in the body causes the tissues of the vagina to shrink and become thin and dry. These tissues may tear or bleed. With ERT, the vagina is more elastic and secretions return to almost normal premenopausal levels in 4 to 6 months. There is also a return of normal moisture in the vagina in response to sexual arousal.

• Bladder symptoms, such as painful urination and frequency.

• Sagging skin and wrinkles.

Disadvantages of ERT

Endometrial Cancer (cancer of the lining of the uterus): Women treated with estrogen alone, who are not given progesterone together with estrogen, face a slightly increased risk for endometrial cancer. Women treated with a combination of estrogen and progesterone are at an even lower risk for this cancer than women who are not treated at all.

Breast Cancer: Studies are still being performed to determine if ERT increases a woman's risk for breast cancer. Discuss this possible risk with your doctor.

Vaginal Bleeding: Women taking a combination of estrogen and progesterone may continue to get menstrual-type withdrawal bleeding from these hormones. However, this bleeding often fades over time.