Older age, higher body weight, lower physical activity, and smoking are all associated with a higher risk of VTE with oral estrogen therapy. Risk of VTE with estrogen therapy is highest at the start of treatment, particularly during the first year, and decreases over time.The absolute risk of VTE with estrogen and/or progestin therapy is small. Women who are not on a birth control pill or hormone therapy have a risk of VTE of about 1 to 5 out of 10,000 women per year. In women taking a birth control pill containing ethinylestradiol and a progestin, the risk of VTE is in the range of 3 to 10 out of 10,000 women per year. Birth control pills containing estradiol valerate and a progestin are associated with about half the risk of VTE of ethinylestradiol/progestin-containing birth control pills. Hormone therapy for transgender women likewise is associated with a lower risk of VTE than birth control pills containing ethinylestradiol and a progestin. The risk of VTE during pregnancy, when estrogens and progesterone increase to very high levels, is 5 to 20 in 10,000 women per year, while the risk is 40 to 65 per 10,000 women per year during the postpartum period. Long-term effects
Uncommon but serious possible side effects of estrogens associated with long-term therapy may include breast cancer, uterine cancer, stroke, heart attack, blood clots, dementia, gallbladder disease, and ovarian cancer.
Cloxestradiol acetate and promestriene are ether prodrugs of estradiol that have been introduced for medical use as estrogens as well, although they are little known and rarely used.Synthetic derivatives of estradiol used as estrogens include ethinylestradiol, ethinylestradiol sulfonate, mestranol, methylestradiol, moxestrol, and quinestrol, all of which are 17α-substituted estradiol derivatives. Synthetic derivatives of estradiol used in scientific research include 8β-VE2 and 16α-LE2. History
Estradiol was first discovered and synthesized in 1933 via reduction of estrone. Subsequently, estradiol was isolated for the first time in 1935. It was also originally known as dihydroxyestrin, dihydrofolliculin, or alpha-estradiol.Estradiol was first introduced for medical use, in the form of estradiol benzoate, a short-acting ester prodrug of estradiol administered by intramuscular injection in oil solution, under the brand name Progynon B in 1933. Estradiol itself was also marketed in the 1930s and 1940s in the form of oral tablets and solutions, vaginal suppositories, and topical ointments under a variety of brand names including Dimenformon, Gynoestryl, Ovocyclin, Progynon, and Progynon DH. Marketed vaginal estradiol suppositories were also used rectally. Estradiol dipropionate, another short-acting ester of estradiol in oil solution for use by intramuscular injection, was marketed under the brand name Di-Ovocylin by 1939. In contrast to estrone, estradiol was never marketed in oil solution for intramuscular injection.