Hormone receptors and, specifically, estrogen receptors were described about four decades ago. For estrogens, there are two receptors, estrogen receptor alpha (ERalpha) and estrogen receptor beta (ERbeta). The two receptors are coded by different genes and their tissue expression varies across organs. ERalpha is predominantly expressed in reproductive tissues (uterus, breast, ovaries) liver and central nervous system, whereas ERbeta is expressed in other tissues such as bone, endothelium, lungs, urogenital tract, ovaries, central nervous system and prostate. More than seventy molecules that belong to the SERMS class have been described. There are 5 chemical groups: triphenylethylenes, benzotiophenes, tetrahydronaphtylenes, indoles and benzopyrans. All of these non-hormonal compounds are capable of activating the ER, reduce bone turnover rate and, as an antiresorptive, clearly improve bone density. Estrogens reduce bone turnover rate and, as an antiresorptive, clearly improve bone density. They are also beneficial for the relief of menopausal symptoms. An ongoing debate that extends over the decades, relates to to overall benefit/risk profile of estrogen or estrogen-progestin therapy since these therapies can increase the risk of serious health disorders, such as breast cancer. SERMs have increased our understanding of hormone-receptor regulatory mechanisms. Their development has permitted a targeted efficacy profile avoiding some of the side effects of the hormone therapy. Their clinical utility relies today mostly on the effects on breast cancer and bone.
Raloxifene; Tamoxifene; Estrogen receptors; Bone turnover; Breast cancer
