A synthetic form of estradiol, a steroid sex hormone vital to the maintenance of fertility and secondary sexual characteristics in females, that may be used as hormone replacement therapy. Typically esterified, estradiol derivatives are formulated for oral, intravaginal, transdermal, or parenteral administration. As the primary, most potent estrogen hormone produced by the ovaries, estradiol binds to and activates specific nuclear receptors. Estradiol exhibits mild anabolic and metabolic properties, and increases blood coagulability. It may play a role in immune and inflammatory processes.