Heart Disease and Hormone Replacement Therapy in Women

For many years, women were prescribed hormone replacement therapy (HRT) as a safeguard against cardiovascular diseases in the menopausal years. The theory was that since younger women suffered from cardiovascular disease far less than older, perhaps the hormones of the younger woman were protective against such diseases. Therefore, it made sense to prescribe replacement hormones for women during menopause. Protecting against heart and vascular diseases is very important as women age. Heart disease is the number one killer of women in America. One in three American women will die from heart disease. Heart disease is also a major cause of disability and decreased quality of life as women age. For all of these reasons, there has been a growing interest in controlling heart and vascular disease in women and HRT was thought to be of great promise.

In 1983, a large study known as HERS (Heart and Estrogen-progestin Replacement Study) was begun to study the effects of HRT on menopausal women with known heart disease. That study found that HRT was not protective against heart attacks and actually increased the number of heart attacks in the first year of HRT. After one year the incidence of heart attacks decreased back to normal. In 1993 another study was launched to look at the issue of the effects of HRT on cardiovascular diseases in healthy menopausal women. This large, thorough study, sponsored by the National Heart, Lung and Blood Institute, was undertaken to determine if HRT consisting of a combination of estrogen and progestin protected women from heart attack and stroke. This study was called the Women’s Health Initiative (WHI) and its results shocked the medical community and patients across the globe. Not only was the treatment of HRT not protective against stroke or heart disease, but participants actually had a higher chance of stroke or heart disease if they took the HRT versus those that only took placebo.

Details of the WHI Study

Women in the study were either given HRT or a placebo and various health measures of each woman were recorded over the following years. The HRT that was given has the brand name of PremPro and the only dosage and formulation available at the time was the most popular form of HRT and was used by nearly 6 million women daily. Each PremPro tablet consisted of 0.625 mg of conjugated equine estrogens (derived from horses) and 2.5 mg of medroxyprogesterone acetate and one tablet was taken daily. Not only cardiovascular disease was tracked but also the incidences of certain cancers and osteoporosis.

Results of the Cardiovascular Part of the Study

Coronary Heart Disease

HRT did not protect against coronary heart disease such as heart attacks. In fact, the rate of heart attacks in women taking HRT was higher than that of women taking placebo. Per 10,000 women on combination HRT, 37 had heart attacks versus 30 of those women taking only placebo. Women taking HRT in the study experienced a 24% overall increase in coronary heart disease versus those women taking placebo. In the first year after starting HRT, the increased risk of developing coronary heart disease was 81% versus women taking placebo. Per 10,000 women on HRT, 36 had heart attacks versus 30 in the placebo group. Women with higher LDL cholesterol at the start of the study were at particularly high risk of developing heart disease.

The final conclusions regarding HRT and heart disease were:

�HRT should not be started or continued to prevent heart disease
�The risk of developing heart disease from HRT outweighs the benefits of decrease in hip fracture and decrease in colon cancer


The risk of stroke was increased by HRT. After an average of 5.6 years, 1.8% of the women on HRT and 1.3% of the women on placebo had strokes. These strokes were primarily caused by blood clots in the brain (the most common type of stroke). For every 10,000 women studied, 29 in the HRT group had strokes versus 21 in the placebo group. This increased risk was the same in every subgroup of women tested.

Peripheral Arterial Disease and Blood Clots

Peripheral arterial disease refers to the narrowing and hardening of blood vessels of the legs, arms and other parts of the body. Analysis of the WHI study has shown that HRT neither increases nor decreases the risk of peripheral arterial disease.

Risk of blood clots in the legs or lungs was dramatically increased by the use of HRT. Risk of clots was the greatest during the first 2 years of hormone use: Women taking HRT had a four-time greater risk of developing the potentially deadly clots than those women using placebo. By the end of the study, the rate of blood clots in HRT users had decreased to become double that of the placebo users. This end rate reflects the fact that of 10,000 women using HRT, 34 would develop blood clots versus only 16 of 10,000 women using placebo.

Overall conclusion

HRT is of NO benefit in protecting the postmenopausal woman from cardiovascular disease. In fact, the most widely used combination therapy HRT appears to increase the risk of heart attack, stroke and blood clots and should be used with caution.

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