Estrogen protects premenopausal women from developing artery-clogging plaques that can cause heart attack and stroke-a protection they lose after menopause. Adding estrogen through hormone replacement therapy (HRT) should restore this protection, but surprisingly, it has no effect on the heart. Physicians have long been aware of the connection between estrogen monotherapy and breast cancer. A study in the July 3 issue of the European Heart Journal found that HRT doubles the risk of blood clots in the veins (venous thromboembolism, or VTE) and can increase the risk of blood clots in the lungs (pulmonary embolism) by 74 percent. "Estrogen is a great medication for osteoporosis and menopausal symptoms, but as a cardiologist, I cant recommend it," says Leslie Cho, MD, head of the Womens Cardiovascular Center at Cleveland Clinic.