ethinyl estradiol or ethy·nyl·es·tra·di·ol .eth-ə-nil-.es-trə-'dī-.ȯl, -.ōl or chiefly Brit ethi·nyl·oes·tra·di·ol or ethy·nyl·oes·tra·di·ol .eth-ə-nil-.ē-strə-'dī-.ȯl, -ē-'strad-ē-.ȯl, -.ōl n a white crystalline very potent synthetic estrogen C20H24O2 prepared from estrone and used in combination (as with norgestrel or norethindrone) as a birth control pill or alone in the treatment of menopausal symptoms or female hypogonadism or in the palliative treatment of prostate or breast cancer see ORTHO-NOVUM, ortho tri-cyclen
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see under ethinyl.Medical dictionary. 2011.