Ethinyl estradiol

Ethinyl estradiol, also sometimes written as 17α-ethinyl estradiol, ethinylestradiol, ethynyl estradiol, or ethinyl œstradiol, is a derivative of 17β-estradiol (E2), the major endogenous estrogen in humans. EE2 is an orally bioactive estrogen used in many formulations of combined oral contraceptive pills and is one of the most commonly used medications for this purpose.