Selective estrogen receptor modulators and bone health

Selective estrogen receptor modulators (SERMs) are synthetic molecules that bind to the estrogen receptor and can have agonistic activity in some tissues while being estrogen antagonistic in others. While not all SERMs are clinically available in all parts of the world, this article will review preclinical and clinical effects of various SERMs on bone. These include tamoxifen, used as adjuvant therapy in breast cancer patients as well as for breast cancer prevention; raloxifene, approved for osteoporosis prevention and treatment as well as breast cancer prevention; bazedoxifene, approved for prevention of osteoporosis and also in combination with conjugated equine estrogen for treatment of vasomotor symptoms and prevention of bone loss in postmenopausal patients; and ospemifene, approved for treatment of dyspareunia due to vulvovaginal atrophy/genitourinary syndrome of menopause. Thus, these SERMs are a diverse group of estrogen agonist/antagonists that seem to have class effects in the bone and breast, although the amount of clinical trial data is quite variable. However, there does not seem to be the same unidirectional class activity in tissues like the uterus or vagina. Health-care providers should be cognizant of all available information in helping patients make the best possible shared decision-making choices.