page_title: Transgender hormone therapy (male-to-female)
section_title: Estrogens
hierarchical_section_title: Transgender hormone therapy (male-to-female) / Medications / Estrogens
caption_attribution_description: English: Estradiol and testosterone levels over the course of 12&#160;weeks following a single intramuscular injection of 320&#160;mg polyestradiol phosphate in men. Created from source material using WebPlotDigitizer and Plotly. Source of the values: &#32;(May 1996).&#32;"Pharmacokinetics and testosterone suppression of a single dose of polyestradiol phosphate (Estradurin) in prostatic cancer patients". Prostate&#32;28&#32;(5): 307–10. DOI:&lt;307::AID-PROS6&gt;3.0.CO;2-8 10.1002/(SICI)1097-0045(199605)28:5&lt;307::AID-PROS6&gt;3.0.CO;2-8. PMID 8610057.
context_page_description: Transgender hormone therapy of the male-to-female type, also known as transfeminine hormone therapy, is hormone therapy and sex reassignment therapy to change the secondary sexual characteristics of transgender people from masculine or androgynous to feminine. It is one of two types of transgender hormone therapy and is predominantly used to treat transgender women and other transfeminine individuals. Some intersex people also take this form of therapy, according to their personal needs and preferences.
  The purpose of the therapy is to cause the development of the secondary sex characteristics of the desired sex, such as breasts and a feminine pattern of hair, fat, and muscle distribution. It cannot undo many of the changes produced by naturally occurring puberty, which may necessitate surgery and other treatments to reverse. The medications used for the MTF therapy include estrogens, antiandrogens, progestogens, and gonadotropin-releasing hormone modulators.
context_section_description: Estrogens are the major sex hormones in women, and are responsible for the development and maintenance of feminine secondary sexual characteristics, such as breasts, wide hips, and a feminine pattern of fat distribution. Estrogens act by binding to and activating the estrogen receptor (ER), their biological target in the body. A variety of different forms of estrogens are available and used medically. The most common estrogens used in transgender women include estradiol, which is the predominant natural estrogen in women, and estradiol esters such as estradiol valerate and estradiol cypionate, which are prodrugs of estradiol. Conjugated estrogens (Premarin), which are used in menopausal hormone therapy, and ethinylestradiol, which is used in birth control pills, have been used in transgender women in the past, but are no longer recommended and are rarely used today due to their higher risks of blood clots and cardiovascular problems. Estrogens may be administered orally, sublingually, transdermally/topically (via patch or gel), rectally, by intramuscular or subcutaneous injection, or by an implant. Parenteral (non-oral) routes are preferred, owing to a minimal or negligible risk of blood clots and cardiovascular issues.
  In addition to producing feminization, estrogens have antigonadotropic effects and suppress gonadal sex hormone production. They are mainly responsible for the suppression of testosterone levels in transgender women. Levels of estradiol of 200 pg/mL and above suppress testosterone levels by about 90%, while estradiol levels of 500 pg/mL and above suppress testosterone levels by about 95%, or to an equivalent extent as surgical castration and GnRH modulators. Lower levels of estradiol can also considerably but incompletely suppress testosterone production. When testosterone levels are insufficiently suppressed by estradiol alone, antiandrogens can be used to suppress or block the effects of residual testosterone. Oral estradiol often has difficulty adequately suppressing testosterone levels, due to the relatively low estradiol levels achieved with it.
  Prior to orchiectomy (surgical removal of the gonads) or sex reassignment surgery, the doses of estrogens used in transgender women are often higher than replacement doses used in cisgender women. This is to help suppress testosterone levels. The Endocrine Society (2017) recommends maintaining estradiol levels roughly within the normal average range for premenopausal women of about 100 to 200 pg/mL. However, it notes that these physiological levels of estradiol are usually unable to suppress testosterone levels into the female range. A 2018 Cochrane review proposal questioned the notion of keeping estradiol levels lower in transgender women, which results in incomplete suppression of testosterone levels and necessitates the addition of antiandrogens. The review proposal noted that high-dose parenteral estradiol is known to be safe. The Endocrine Society itself recommends dosages of injected estradiol esters that result in estradiol levels markedly in excess of the normal female range, for instance 10 mg per week estradiol valerate by intramuscular injection. A single such injection results in estradiol levels of about 1,250 pg/mL at peak and levels of around 200 pg/mL after 7 days. Dosages of estrogens can be reduced after an orchiectomy or sex reassignment surgery, when gonadal testosterone suppression is no longer needed.
caption: Estradiol and testosterone levels over 12 weeks after a single intramuscular injection of 320 mg polyestradiol phosphate, a polymeric estradiol ester and prodrug, in men with prostate cancer.[14] Demonstrates the suppression of testosterone levels by parenteral estradiol.
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