Used in hormone replacement therapy to alleviate symptoms of menopause such as hot flashes, vaginal dryness, and mood changes. Also prescribed for treating low estrogen levels in women with ovarian failure or certain genetic conditions. Commonly included in transgender hormone therapy for feminization. Applied in some cases to prevent osteoporosis in postmenopausal women at high risk. Found in certain contraceptive formulations to regulate menstrual cycles and suppress ovulation. Used in research settings to study estrogen receptor activity and hormone-sensitive cancers.