Postmenopausal Hormone Therapy Increases Blood Clot Risk

(Ivanhoe Newswire) -- Postmenopausal women who have had their uterus removed and are on estrogen therapy may have a higher risk of venous thrombosis (VT) -- the formation of blood clots in the veins.

A new study from the University of Hawaii and Pacific Health Research Institute in Honolulu analyzed data from a Women's Health Initiative (WHI) trial that examined the effect of estrogen alone in women ages 50 to 79. In the WHI trial, participants took either combined equine estrogens (a mix of several estrogens) or a placebo. They were followed for an average of 7.1 years.

Results show 197 women developed VT, including 144 with deep vein thrombosis, 91 with pulmonary embolism and 38 with both.

Of the 197, 111 were taking estrogen and 86 were on a placebo. Researchers found the risk of VT was slightly higher for women on estrogen therapy. It significantly increased deep venous thrombosis. The risk was highest in the first two years of therapy. Estrogen created a greater risk in women who were more physically active and those with lower HDL cholesterol.

"Our data suggest that although the absolute incidence is relatively low, the use of combined equine estrogens increases the relative risk of venous thrombosis in postmenopausal women without a uterus," study authors say.

Researchers also say, "Women with appropriate indications, such as short-term treatment of severe menopausal symptoms, should use combined equine estrogens only after careful consideration of the relative risks and benefits, especially if the women have other risk factors for venous thrombosis."

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SOURCE: Archives of Internal Medicine, 2006;166:772-780

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