Esterified Estrogens and Conjugated Equine Estrogens and the Risk of Venous Thrombosis

Abstract

Clinical trial evidence from the Heart and Estrogen/progestin Replacement Study (HERS) and the Women’s Health Initiative (WHI) indicates that estrogen therapy, with or without progestins, is associated with an increased risk of venous thrombosis (VT) in postmenopausal women.^1-3 The HERS investigators observed a relative risk of 2.7 (95% confidence interval [CI], 1.4-5.0) for estrogen plus progestin therapy, and the WHI investigators observed a relative risk of 2.1 (95% CI, 1.6-2.8) and 1.3 (95% CI, 1.0-1.8) for estrogen with and without concomitant progestin use, respectively. Each of these trials evaluated oral conjugated equine estrogens (CEEs) and medroxyprogesterone acetate.