<unk> , sold under the brand names Enovid, Norinyl, and Ortho-Novum among others, is an estrogen medication which has been used in birth control pills, menopausal hormone therapy, and the treatment of menstrual disorders. It is formulated in combination with a progestin and is not available alone. It is taken by mouth. Side effects of<unk>  include nausea, breast tension, edema, and breakthrough bleeding among others. It is an estrogen, or an agonist of the estrogen receptors, the biological target of estrogens like estradiol.<unk>  is a prodrug of ethinylestradiol in the body.<unk>  was discovered in 1956 and was introduced for medical use in 1957. It was the estrogen component in the first birth control pill. In 1969,<unk>  was replaced by ethinylestradiol in most birth control pills, although<unk>  continues to be used in a few birth control pills even today.<unk>  remains available only in a few countries, including the United States, United Kingdom, Japan, and Chile.
Mestranol
Hexestrol
Gestodene
Fosfestrol
Moxestrol
Allenestrol
Dimestrol
Dienestrol