Estradiol (E2), also called oestrogen, oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of female reproductive cycles such as estrous and menstrual cycles. Estradiol is an estrogen hormone. The hormone from the patch, gel, and spray is absorbed through your skin into your body. This medicine is available only with your doctor's prescription. Learn about the side effects of estradiol, from common to rare, for consumers and healthcare professionals. Estradiol (E2) is the most potent and clinically measured form of estrogen. It is produced primarily in the ovaries in women, in small amounts by the testes in men, and in fat tissue in both sexes. Estradiol is a form of estrogen, a female sex hormone that regulates many processes in the body. It is available as an oral tablet, a topical gel or patch, vaginal cream, or as an injection. It can be used to prevent osteoporosis after menopause. It is also used to reduce the symptoms of late-stage breast or prostate cancer. It works by increasing levels of the hormone estrogen in the body. This medication is an estrogen hormone. Cleveland Clinic is a non-profit academic medical center. Find patient medical information for Estradiol (Delestrogen, Depo-Estradiol, Estrace) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings.