Estrogen receptor β -: a new dimension in estrogen mechanism of action

Cloning of the novel estrogen receptor β (ERβ) has led to a paradigm shift in our understanding of estrogen action. The concept of a second estrogen receptor with somewhat different ligand binding specificity than the previously known receptor (ERα) opens up the possibility for development of novel estrogenic drugs that might distinguish between the two receptors. This could be of importance in treatment of various diseases, as the two receptors seem to be differentially expressed in several tissues. ERβ appears to be very important in the central nervous system, bone, lung, urogenital tract, cardiovascular system, ovary, testis, kidney and colon. The physiological function of ERβ is under intense study but certain results indicate that ERα and ERβ have different or even opposite biological actions.