Estradiol valerate (EV), sold for use by mouth under the brand name Progynova and Primiwal E4 and for use by injection under the brand names Delestrogen and Progynon Depot among others, is an estrogen medication. It is used in hormone therapy for menopausal symptoms and low estrogen levels, hormone therapy for transgender people, and in hormonal birth control. It is also used in the treatment of prostate cancer. The medication is taken by mouth or by injection into muscle or fat once every 1 to 4 weeks. Side effects of estradiol valerate include breast tenderness, breast enlargement, nausea, headache, and fluid retention. Estradiol valerate is an estrogen and hence is an agonist of the estrogen receptor, the biological target of estrogens like estradiol. It is an estrogen ester and a prodrug of estradiol in the body. Because of this, it is considered to be a natural and bioidentical form of estrogen. Estradiol valerate was first described in 1940 and was introduced for medical use in 1954. Along with estradiol cypionate, it is one of the most widely used esters of estradiol. Estradiol valerate is used in the United States, Canada, Europe, and throughout much of the rest of the world. It is available as a generic medication. Medical uses The medical uses of estradiol valerate are the same as those of estradiol and other estrogens. Examples of indications for the medication include hormone therapy and hormonal contraception. In regard to the latter, estradiol valerate is available in combination with a progestin as a combined estradiol-containing oral contraceptive (with dienogest) and as a combined injectable contraceptive. Along with estradiol cypionate, estradiol undecylate, and estradiol benzoate, estradiol valerate is used as a form of high-dose estrogen therapy in feminizing hormone therapy for transgender women. It is also used as a form of high-dose estrogen therapy in the treatment of prostate cancer in men. Low-dose oral estradiol valerate (2–6 mg/day) has been used in the treatment of breast cancer in women who were previously treated with and benefited from but acquired resistance to aromatase inhibitors as well. Injectable estradiol valerate has been used to suppress sex drive in sex offenders. In the United States, the approved indications of estradiol valerate injections include the treatment of moderate to severe hot flashes and vaginal atrophy associated with menopause in women, the treatment of hypoestrogenism due to hypogonadism, castration, or primary ovarian failure in women, and