Synthetic Estrogens Pose Greater Clot Risk Than Natural Forms of Hormone

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In a head-to-head comparison of two major forms of hormone replacement therapy, a more natural version of estrogen proved less dangerous to the heart than a synthetic one made from the urine of pregnant mares.

While previous studies linked hormone therapy to a higher risk of breast cancer and heart disease, few looked at whether different forms of the hormone made a difference in the magnitude of these risks. So scientists from the University of Washington, Seattle studied 384 postmenopausal women between the ages of 30 and 79 who were using either conjugated equine estrogens (CEEs), or estradiol a natural, bioequivalent form of the hormone.

After monitoring the women for vascular events such as blood clots, heart attacks, and strokes between January 2003 and December 2009, they found that 68 women developed blood clots, 67 women had a heart attack and 48 women experienced a clot-related stroke. Only the risk of blood clots was statistically significant, but the researchers say that the type of estrogen pill a post-menopausal women chooses may affect her circulation and risk of vessel disorders. Women should therefore discuss the different types of hormone therapies available with their doctors, and assess the risks and benefits of each before deciding which one is appropriate for them.