Ethinylestradiol (EE) is an estrogen obtained by substituting an hydrogen atom at the 17α position of estradiol with an ethynyl group. In a case report, 60 μg/day EE maximally suppressed testosterone levels in one transgender woman. Common brand names used for EE include Diane-35 and Ginette-35, each pill contains 35 μg of EE and 2 mg of cyproterone acetate (CPA). EE has a much higher risk of blood clots and cardiovascular issues than oral estradiol and particularly non-oral estradiol. EE was used in transfeminine hormone therapy in the past, but has been largely abandoned due to its greater health risks and is no longer recommended. The risks of EE are especially prominent in those with known propensity to blood clots, those over 40 years of age, and when higher doses are used.
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