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Hormones affect heart

3 min read

DEAR DOCTOR K: I’m 68 years old and have been on low-dose estrogen therapy since I had a hysterectomy (and started menopause) at age 50. My doctor won’t prescribe it anymore because he says it increases my risk of heart problems. Is that true?

DEAR READER: The effect of hormone therapy on the heart is a controversial area. Hormone therapy usually involves “combination therapy,” with both estrogens (the main female hormones) and progestins (other important female hormones). Estrogen helps reduce symptoms of menopause, such as hot flashes. Progestin reduces the risk of cancer of the uterus.

In my opinion, combination therapy or estrogen therapy alone probably reduces the risk of heart disease among women entering menopause, and for five to 10 years thereafter. But then, about 10 years after menopause, combination hormone therapy begins to increase the risk of heart disease. So your doctor has reason to be concerned.

How could it be that hormone therapy protects against heart disease in younger menopausal women, but increases the risk of heart disease in older menopausal women? Why should age matter? It has to do with the effect of female hormones on blood vessels.

The most common type of heart disease is atherosclerosis of the arteries that supply blood to the heart. Atherosclerosis causes cholesterol-filled “plaques” in the walls of the arteries. As these plaques grow, they can block the flow of blood through the arteries. When blood flow to a part of the heart muscle stops, the muscle dies. That’s what happens in a heart attack.

Some heart attacks are caused by plaques that slowly grow and finally become so large that they shut off the blood supply to a part of the heart. However, more heart attacks are caused by smaller plaques. These plaques are not large enough to block blood flow very much.

But each plaque has a cap of fibers that holds in the plaque’s pool of cholesterol. In some plaques, called “vulnerable plaques,” inflammation inside the plaque eats away at the fibrous cap. Suddenly, the fibers rupture, cholesterol spills into the artery, a blood clot forms — and blood flow to a part of the heart stops.

Estrogen slows the development of plaques. By the time a woman reaches menopause, her own natural estrogen has helped protect her against developing plaques. The estrogen in hormone therapy continues to slow (but not stop) plaque development.

By 10 years after menopause, however, the average woman has vulnerable plaques that threaten to rupture. Estrogen increases inflammation inside the plaques, and it causes blood to clot more easily. So estrogen now increases the risk of heart attacks.

Most studies that show an increased risk of heart disease in women of your age involved the use of combination hormone therapy. You’re on just estrogen, and a low dose at that. Still, I think the safest assumption is that you are at a somewhat increased risk. You and your doctor have to balance the risk against any benefits you feel you get from estrogen.

(Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.)

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