Feminizing hormone therapy
Feminizing hormone therapy, also known as transfeminine hormone therapy, is a form of gender-affirming care and a gender-affirming hormone therapy to change the secondary sex characteristics of transgender people from masculine to feminine. It is a common type of transgender hormone therapy and is used to treat transgender women and non-binary transfeminine individuals. Some, in particular intersex people, but also some non-transgender people, 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 feminizing hormone therapy include estrogens, antiandrogens, progestogens, and gonadotropin-releasing hormone modulators.
Feminizing hormone therapy has been empirically shown to reduce the distress and discomfort associated with gender dysphoria in transfeminine individuals.
Requirements
Many physicians operate by the World Professional Association of Transgender Health Standards of Care model and require psychotherapy and a letter of recommendation from a psychotherapist in order for a transgender person to obtain hormone therapy. Other physicians operate by an informed consent model and have no requirements for transgender hormone therapy aside from consent.Medications used in transgender hormone therapy are also sold without a prescription on the Internet by unregulated online pharmacies, and some transgender women purchase these medications and treat themselves using a do-it-yourself or self-medication approach. One reason that many transgender people turn to DIY hormone therapy is due to long waiting lists of up to years for standard physician-based hormone therapy in some parts of the world such as the United Kingdom, as well as due to the often high costs of seeing a physician and the restrictive criteria that make some ineligible for treatment, or simply medical malpractice by physicians that are not adequately trained.
The accessibility of transgender hormone therapy differs throughout the world and throughout individual countries.
Medications
A variety of different sex-hormonal medications are used in feminizing hormone therapy for transgender women. These include estrogens to induce feminization and suppress testosterone levels; antiandrogens such as androgen receptor antagonists, antigonadotropins, GnRH modulators, and 5α-reductase inhibitors to further oppose the effects of androgens like testosterone; and progestogens for various possible though uncertain benefits. An estrogen in combination with an antiandrogen is the mainstay of feminizing hormone therapy for transgender women.Estrogens
s 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, 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, 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, rectally, by intramuscular or subcutaneous injection, or by an implant. Parenteral routes are practically preferred, owing to a minimal or negligible risk of blood clots and cardiovascular issues.The pharmacokinetics of estradiol's routes of administration vary greatly. Sublingual and rectal administration result in peak concentrations up to ten times higher than oral administration, and higher trough concentrations. This makes frequent, small sublingual or rectal doses, a very efficient way to create a stable and constant increase in trough levels. A large amount of estradiol consumed sublingually, and especially orally is converted by the GI tract into estrone and other compounds, causing a higher estrone:estradiol ratio. This means oral doses are more subject to individual variances in enzymes and physiological chemistry. The extent of the estrone ratio's effects are unclear but, as a weaker estrogen agonist than estradiol, a high estrone level can reduce feminization by competitive antagonism. A high estrone ratio is linked to reduced skeletal growth in pubertal boys and insulin resistance in PCOS. The ratio is also known to be higher in early female puberty, and lower in the later stages. An average dose intramuscular injection can vary from far above to far [|below] the average female range over the course of a week, depending on an individual's body.
In addition to producing feminization, estrogens have antigonadotropic effects, suppressing testosterone and other gonadal sex hormones. 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 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 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.
File:Estradiol and testosterone levels with a single intramuscular injection of 320 mg polyestradiol phosphate in men.png|thumb|right|350px|class=skin-invert-image|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. Demonstrates the suppression of testosterone levels by parenteral estradiol.
Antiandrogens
s are medications that prevent the effects of androgens in the body. Androgens, such as testosterone and dihydrotestosterone, are the major sex hormones in individuals with testes, and are responsible for the development and maintenance of masculine secondary sex characteristics, such as a deep voice, broad shoulders, and a masculine pattern of hair, muscle, and fat distribution. In addition, androgens stimulate sex drive and the frequency of spontaneous erections and are responsible for acne, body odor, and androgen-dependent scalp hair loss. Androgens also have functional antiestrogenic effects in the breasts and oppose estrogen-mediated breast development, even at low levels. Androgens act by binding to and activating the androgen receptor, their biological target in the body. Antiandrogens work by blocking androgens from binding to the androgen receptor and/or by inhibiting or suppressing the production of androgens.Antiandrogens that directly block the androgen receptor are known as androgen receptor antagonists or blockers, while antiandrogens that inhibit the enzymatic biosynthesis of androgens are known as androgen synthesis inhibitors and antiandrogens that suppress androgen production in the gonads are known as antigonadotropins. Estrogens and progestogens are antigonadotropins and hence are functional antiandrogens. The purpose of the use of antiandrogens in transgender women is to block or suppress residual testosterone that is not suppressed by estrogens alone. Additional antiandrogen therapy is not necessarily required if testosterone levels are in the normal female range or if the person has undergone orchiectomy. However, individuals with testosterone levels in the normal female range and with persisting androgen-dependent skin and/or hair symptoms, such as acne, seborrhea, oily skin, or scalp hair loss, can potentially still benefit from the addition of an antiandrogen, as antiandrogens can reduce or eliminate such symptoms.
Steroidal antiandrogens
s are antiandrogens that resemble steroid hormones like testosterone and progesterone in chemical structure. They are the most commonly used antiandrogens in transgender women. Spironolactone, which is relatively safe and inexpensive, is the most frequently used antiandrogen in the United States. Cyproterone acetate, which is unavailable in the United States, is widely used in Europe, Canada, and the rest of the world. Medroxyprogesterone acetate, a similar medication, is sometimes used in place of cyproterone acetate in the United States.File:Testosterone levels with estradiol alone, estradiol plus spironolactone, and estradiol plus cyproterone acetate in transfeminine people.png|thumb|right|350px|class=skin-invert-image|Testosterone levels with estradiol alone or in combination with an antiandrogen in the form of spironolactone or cyproterone acetate in transfeminine people. Estradiol was used in the form of oral estradiol valerate in almost all cases. The dashed horizontal line is the upper limit of the female/castrate range.
Spironolactone is an antimineralocorticoid and potassium-sparing diuretic, which is mainly used to treat high blood pressure, edema, high aldosterone levels, and low potassium levels caused by other diuretics, among other uses. Spironolactone is an antiandrogen as a secondary and originally unintended action. It works as an antiandrogen mainly by acting as an androgen receptor antagonist. The medication is also a weak steroidogenesis inhibitor, and inhibits the enzymatic synthesis of androgens. However, this action is of low potency, and spironolactone has mixed and inconsistent effects on hormone levels. In any case, testosterone levels are usually unchanged by spironolactone. Studies in transgender women have found testosterone levels to be unaltered with spironolactone or to be decreased. Spironolactone is described as a relatively weak antiandrogen. It is widely used in the treatment of acne, excessive hair growth, and hyperandrogenism in women, who have much lower testosterone levels than men. Because of its antimineralocorticoid activity, spironolactone has antimineralocorticoid side effects and can cause high potassium levels. Hospitalization and/or death can potentially result from high potassium levels due to spironolactone, but the risk of high potassium levels in people taking spironolactone appears to be minimal in those without risk factors for it. As such, monitoring of potassium levels may not be necessary in most cases. Spironolactone has been found to decrease the bioavailability of high doses of oral estradiol. Although widely employed, the use of spironolactone as an antiandrogen in transgender women has recently been questioned due to the various shortcomings of the medication for such purposes.
Cyproterone acetate is an antiandrogen and progestin which is used in the treatment of numerous androgen-dependent conditions and is also used as a progestogen in birth control pills. It works primarily as an antigonadotropin, secondarily to its potent progestogenic activity, and strongly suppresses gonadal androgen production. Cyproterone acetate at a dosage of 5 to 10 mg/day has been found to lower testosterone levels in men by about 50 to 70%, while a dosage of 100 mg/day has been found to lower testosterone levels in men by about 75%. The combination of 25 mg/day cyproterone acetate and a moderate dosage of estradiol has been found to suppress testosterone levels in transgender women by about 95%. In combination with estrogen, 10, 25, and 50 mg/day cyproterone acetate have all shown the same degree of testosterone suppression. In addition to its actions as an antigonadotropin, cyproterone acetate is an androgen receptor antagonist. However, this action is relatively insignificant at low dosages, and is more important at the high doses of cyproterone acetate that are used in the treatment of prostate cancer. Cyproterone acetate can cause elevated liver enzymes and liver damage, including liver failure. However, this occurs mostly in prostate cancer patients who take very high doses of cyproterone acetate; liver toxicity has not been reported in transgender women. Cyproterone acetate also has a variety of other adverse effects, such as fatigue and weight gain, and risks, such as blood clots and benign brain tumors, among others. High dosages of cyproterone-based medication have been linked with meningioma. Periodic monitoring of liver enzymes and prolactin levels may be advisable during cyproterone acetate therapy.
Medroxyprogesterone acetate is a progestin that is related to cyproterone acetate and is sometimes used as an alternative to it. It is specifically used as an alternative to cyproterone acetate in the United States, where cyproterone acetate is not approved for medical use and is unavailable. Medroxyprogesterone acetate suppresses testosterone levels in transgender women similarly to cyproterone acetate. Oral medroxyprogesterone acetate has been found to suppress testosterone levels in men by about 30 to 75% across a dosage range of 20 to 100 mg/day. In contrast to cyproterone acetate however, medroxyprogesterone acetate is not also an androgen receptor antagonist. Medroxyprogesterone acetate has similar side effects and risks as cyproterone acetate, but is not associated with liver problems.
Numerous other progestogens and by extension antigonadotropins have been used to suppress testosterone levels in men and are likely useful for such purposes in transgender women as well. Progestogens alone are in general able to suppress testosterone levels in men by a maximum of about 70 to 80%, or to just above female/castrate levels when used at sufficiently high doses. The combination of a sufficient dosage of a progestogen with very small doses of an estrogen is synergistic in terms of antigonadotropic effect and is able to fully suppress gonadal testosterone production, reducing testosterone levels to the female/castrate range.