Coronary heart disease is the major cause of death and disability among women in the developed world. Several observational clinical studies have reported that postmenopausal women who take hormone replacement therapy have lower incidence of coronary heart disease; therefore, hormone replacement therapy has been recommended for secondary prevention of heart disease (which aims to decrease risk of disease recurrence) in postmenopausal women. Initially, estrogen alone was prescribed as hormone replacement therapy. However, progestins (natural or synthetic forms of progesterone) are now added to estrogen for women with an intact uterus in order to reduce, or eliminate, the excess risk for endometrial cancer observed with estrogen alone (unopposed estrogen); this treatment modality is now commonly referred to as combined hormone replacement therapy.