Estrogen receptors (ER) are members of the steroid/thyroid hormone receptor superfamily of ligand-activated transcription factors. Estrogen receptors, including ERα and ERβ, contain DNA binding and ligand binding domains and are critically involved in regulating the normal function of reproductive tissues. They are located in the nucleus , though some estrogen receptors associate with the cell surface membrane and can be rapidly activated by exposure of cells to estrogen. Evidence suggests that ERα and ERβ may be regulated by distinct mechanisms even though they share many functional characteristics.
