Mechanism Estrogen receptor agonist Indications Hypogonadism/ovarian failure Menstrual abnormalities Hormone replacement therapy in postmenopausal women to treat menopausal symptoms e.g. hot flashes, vaginal atrophy osteoporosis estrogens inhibit osteoclast activity Androgen-dependent prostate cancer Contraindications ER-positive breast cancer thrombophilic disorders Toxicity Postmenopausal bleeding Thrombophilia Breast tenderness Increased risk of endometrial cancer when estrogen is unopposed by progesterone CVA clear cell adenocarcinoma of vagina in females exposed to DES in utero presents in late teens breast cancer