Phytoestrogens in the Context of SERMs

Abstract

Selective estrogen receptor modulators (SERMs) are characterized by their ability to act as either estrogen agonists or antagonists in different tissues, with different genes, and in different hormonal milieux. The effects of the most-studied SERMs are partially understood by their interactions with the ligand-binding pocket of the estrogen receptors (ER) α and β, as described elsewhere in this text. Phytoestrogens are plant constituents with a phenol structure similar to estrogen. They are found in a wide variety of edible plants and have acquired the misnomer of “nature’s SERMs.” Although these compounds may exhibit both estrogenic and antiestrogenic effects, the extent to which antiestrogenic effects are caused by ER antagonism is not known. It appears most feasible that they may act as weak estrogens under some circumstances, with apparent antiestrogenic effects resulting from either non ER-mediated mechanisms or their ability to bind ERa and β in the cell and exert weak agonism in the presence of estradiol. Hence the ultimate actions of these compounds in specific cells is determined by many factors including the presence or absence of estradiol, the concentration of the phytoestrogen being studied, the presence or absence of other phytoestrogens, the relative levels of ERα and ERβ, and the diverse mix of coactivators and corepressors present. Effects vary according to the phytoestrogen studied, cell line, tissue, species, and response being evaluated. Furthermore, in attempting to translate in vitro findings to humans, the interindividual diversity and complexity of dietary phytoestrogen absorption and metabolism make the bioactivity of these compounds unpredictable.KeywordsBreast CancerHigh Performance Liquid ChromatographyPostmenopausal WomanVaginal CytologyPhytoestrogen IntakeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.