Overall Mortality Rate

Studies are generally positive regarding the effect of both estrogen and combination replacement therapies on overall mortality. One large study found that women taking HRT had better survival rates than those who were not using HRT; the benefit was greatest in the first 10 years of therapy, after which it diminished somewhat due to an increase in breast cancer in HRT users. Some experts believe that part, although not all, of the lower mortality rates may be due to a healthier lifestyle in general in women who choose hormone replacement therapy.

Effects on Heart Disease

Specific Benefits for the Heart. Estrogen's most well-known beneficial effect for the heart is on cholesterol and other lipids (fatty molecules.) Before menopause, women have healthier cholesterol levels than men. About two years before menopause, the dangerous low-density lipoprotein (LDL) cholesterol levels begin to rise and the advantageous high-density lipoprotein (HDL) levels decrease -- a particular danger for women. Unopposed estrogen therapy has a proven track record in reversing these changes. Because unopposed estrogen increases the risk for uterine cancer, progestins are added for women who would otherwise be at risk for this cancer. The effects on the heart of such combination therapies have been less clear. Some progestins raise LDL and reduce HDL.

At this time, experts recommend that women with existing heart disease not begin taking HRT for protection. Those with heart disease who are on HRT, however, should continue, since they are probably being protected. Such recommendations may change as study results become clearer on the risks and benefits for specific women with existing heart conditions.

Effects on Stroke

The effect of estrogen on the risks for stroke is conflicting. Some studies are showing some protection from stroke, but others have found no or insignificant benefits. Some have even found an increased risk for non-fatal stroke caused by bleeding or thromboembolism, although others have found no evidence to support this. One study unexpectedly found that hormone therapy had no protective benefits on hardening of the carotid artery -- the major artery leading to the brain -- a major cause of stroke.

Effects on Bones and Joints

Osteoporosis. Osteoporosis is a disease of the skeleton in which the amount of calcium present in the bones slowly decreases until the bones become brittle and susceptible to fracture.

 After menopause, calcium depletion accelerates. As much as 6% of calcium is lost per year for as long as 10 years. Estrogen's most important effect appears to be prevention of bone break down. In older women, estrogen therapy prevents the loss in bone density, and major studies are now reporting that women who have received postmenopausal estrogen therapy, with or without progesterone, experience fewer hip fractures as well as fractures of all types than untreated women.

Calcium, magnesium, and vitamin D are important companions to estrogen therapy for prevention and treatment of osteoporosis.

Alzheimer's Disease and Effects on Mental Function

Estrogen appears to have properties that protect against the memory loss and lower mental functioning associated with normal aging. Some studies have reported that women taking hormone replacement therapy (in various combinations) score better on memory and learning than women not on HRT.

Urinary Tract Infections

Women are at increased risk for recurrent urinary tract infections after menopause. One study found that postmenopausal women who used an estrogen vaginal cream had a dramatically lower incidence of recurring infections than women not using the cream. Researchers suggest that estrogen may resist infection by increasing the number of lactobacilli, a microorganism that fights infection by preventing bacteria from adhering to vaginal cells. It is not clear whether taking oral estrogen has the same benefit. Some studies, in fact, reported a higher incidence of urinary tract infections in women taking oral estrogen.

Colorectal Cancer

Studies continue to show that hormone replacement therapy, with or without progesterone, protects against colon cancer. Risk reduction for colon cancer is also associated, however, with a healthy lifestyle, and it is still not yet known whether estrogen protects against colon cancer or if rather women who take HRT tend to be healthier.

Teeth, Eyes, and Skin Problems

Estrogen therapy has been associated with reduced gum bleeding and with decreased bone loss around the teeth, women who take estrogen are less likely to lose their teeth. Thus, the same principle that helps prevent bone loss in osteoporosis is also at work in preventing bone loss in the mouth. Studies are also indicating that estrogen helps prevent glaucoma and macular degeneration. Some evidence exists that estrogen therapy may help prevent slackness and dryness in the skin and even reduce wrinkles. Estrogen creams have proven to be beneficial in tests, reducing fine lines and increasing skin thickness. Estrogen may also have wound-healing properties that may prove to help women with varicose veins.

Diabetes

Studies indicate that HRT may help post-menopausal women with diabetes control their blood sugar levels more effectively. It may even help prevent diabetes type 2 after menopause.