When a person decides to medically transition, the first step is usually to begin taking cross-sex hormones, commonly referred to as “hormone replacement therapy” (HRT) by the medical and transgender community. Cross-sex hormones will be the dominant hormone of the opposite sex to that of the person wanting to transition. For example, if a female wishes to transition to appear as a man, she will take testosterone (“T”). If a male wishes to transition to appear female, he will take estrogen. Cross-sex hormones are considered a controlled substance and must be prescribed by a doctor. Testosterone is commonly taken by intramuscular injection into the leg or buttocks, administered every one to two weeks. Estrogen is usually taken in pill or patch form. Male to female (MtF) transgender people are often prescribed testosterone blockers along with estrogen to allow the estrogen to have a greater impact on the body.
Although cross-sex hormones are powerful drugs, they take time to work on the body. The simplest way to think about it is to think of puberty, and how long that stage can take in most people. Transgender people who medically transition often refer to their transition as a “second puberty”, and for good reason – it takes time and can be a difficult process.
The goal of HRT is to eventually allow the person to appear as the opposite sex. This can take years to achieve, and the results vary widely by person depending on dosage, genetics, and age. Females taking testosterone tend to be able to “pass” as the opposite sex sooner than males who take estrogen. Things that cannot be changed by HRT to that of the opposite sex include height, skeletal structure, genitalia, breasts (in females), genetics, sex chromosomes, and the reproductive system. (This is true for adults who have already gone through a natural puberty with their own biological hormones. For children who are administered hormone blockers and then cross-sex hormones, height, skeletal structure, and breast growth are affected by cross-sex hormones. Genitalia, genetics, and the reproductive system remain in their natural form corresponding to the child’s natal sex.)
FtMs who take testosterone do so to achieve a male appearance. The side effects of testosterone on the female body are not well known by the medical community, due to a lack of research into the use of testosterone in females. The majority of negative side effects are only known from self-reporting, either to a physician or among the FtM and detrans female communities.
The following list shows the most common side effects of testosterone on the female body. The majority of these side effects are desired, with a few exceptions. These are the side effects most commonly recognized by the medical community. https://transcare.ucsf.edu/article/information-testosterone-hormone-therapy
- Voice deepening
- Male pattern facial and body hair
- Clitoral growth
- Fat distribution to a more male pattern
- Ability to gain more muscle mass
- Menstruation stops
- Possible male pattern baldness
- Mood swings
- Body odor change
- Higher libido
- Possible high blood pressure
- Possible diabetes
The following list of side effects have been experienced by trans men and detrans women, usually after prolonged use of testosterone (2 + years). These side effects are generally talked about in private spaces within the trans and detrans community, and are often not acknowledged within the medical community.
- Uterine atrophy and pelvic pain (usually after several years on T)
- Higher cholesterol, leading to higher likelihood of stroke and heart attack
- Vaginal atrophy
- Liver damage
- Muscle scar tissue at injection sites
- Trouble sleeping
- Painful orgasm
No research has been done to attempt to measure the rates of these side effects among female people who take testosterone.
Male to female trans people who take estrogen, progesterone and testosterone blockers do so to achieve a more female appearance. The most common HRT practice includes estrogen along with a testosterone blocker. Some MtF trans people also take progesterone, although there is no substantial evidence to support that this helps the feminization process compared to estrogen and testosterone blockers alone (https://transcare.ucsf.edu/guidelines/feminizing-hormone-therapy). Research into the effects of HRT in males is better understood than FtM HRT. MtF HRT and SRS have a longer, more established history within the medical field. Even so, there are side effects that are not well understood or discussed openly in the medical community. The following list shows the most common and well-understood side effects of MtF HRT.
- Decreased facial and body hair
- Decreased muscle mass
- Redistribution of body fat to more female pattern
- Some breast development, usually not above a small B cup size
- Softening skin
- Decreased libido
- Loss of spontaneous erections
- Mood swings
- Erectile disfunction (ed medications can be taken)
- Blood clots that can result in stroke or even death
- Liver disease
- Weight gain
- High cholesterol which can cause heart disease
- High blood pressure
- Dizziness and dehydration (from testosterone blockers)
The following side effects are not discussed openly with in the medical community, but have anecdotally been observed and experienced.
- Testicular atrophy
- Blood in semen
- Difficulty achieving orgasm
- Decrease or loss of sperm production