Ethinylestradiol

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