Female-to-male (FTM) testosterone therapy, or T therapy, is a treatment that some people may receive to induce “masculine” physical traits and suppress “feminine” ones.

Those who choose to undergo T therapy will receive the hormone testosterone to reduce estrogen production. Estrogen is a hormone associated with the development of typically feminine traits.

There are several potential benefits and risks associated with this therapy. Some people may experience changes within a few months, but certain changes may take a few years to take maximum effect.

This article will replace the term FTM testosterone therapy with the term T therapy. This is because FTM terminology is binary and exclusionary. Not everyone who uses testosterone-based hormone therapy may identify as a woman or have the goal of becoming a man.

This article will discuss T therapy, including the potential risks, the benefits, and what people can expect during and after treatment.

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T therapy is a treatment that induces typically masculine physical traits while suppressing typically feminine ones.

People undergoing T therapy receive the hormone testosterone. This helps decrease estrogen production and suppress menstrual cycles. It can also lead to physical changes, such as male-pattern hair growth and a deepening voice.

Changes due to treatment may be temporary or permanent.

Other names for T therapy may include masculinizing hormone therapy, cross-sex hormone therapy, testosterone-based hormone therapy, and gender affirming hormone therapy.

A person may undergo T therapy if they have gender dysphoria. A person has gender dysphoria when they experience distress because their gender identity does not match their sex assigned at birth.

Testosterone treatment may reduce a person’s gender dysphoria and emotional distress and improve their quality of life. It may also promote the matching of a person’s gender identity and their body and allow them to experience gender congruence.

Undergoing T therapy during adolescence (around the age of 16 years and older) may stop the development of female secondary sex characteristics, such as breasts. It may also induce male secondary sex characteristics, such as facial hair.

Although research is ongoing, some people who wish to undergo T therapy may have difficulty receiving treatment or experience potential complications from it. This includes those who:

Not everyone who experiences gender dysphoria will have T therapy. Although it may have benefits for some people, the treatment is not without risk.

The National Transgender Discrimination Survey Report on Health and Health Care reports that at least 80% of transgender people have either undergone gender affirming hormone therapy or wish to at some point.

People may receive T therapy in a number of ways. These include:

  • testosterone injections
  • oral testosterone
  • transdermal (through the skin) testosterone

In the United States, doctors prescribe the medication and provide guidelines on how to safely administer the therapy.

People typically receive T therapy as an injection, either into a muscle (intramuscular) or under the skin (subcutaneous). Most people will receive the injections weekly, though some people may require higher doses every 10–14 days.

Oral administration of testosterone undecanoate (Jatenzo) involves taking a pill twice daily. Transdermal options are available as a gel (Androgel) or a patch (Androderm). However, doctors are more likely to suggest these options to treat testosterone deficiency.

The age at which a person can access gender affirming hormone therapy varies across the world. For example, in Europe, many countries allow people between the ages of 14 and 18 years to access it, but in some countries, such as Holland, people can access it from the age of 12 years, as long as they have parental consent.

In some other European countries, access depends on the maturity of the person who wishes to receive the therapy.

In the U.S., most people can access T therapy at age 18 years, which is when they are capable of consent. At 17 years old, a person may have access, but they will require a parent or guardian to accompany them to appointments. At age 16 years or younger, additional paperwork is necessary for people to access such therapy.

People may consider T therapy as a second puberty. Although some changes will occur quicker than others, it can take years for the full effect.

Changes may include:

Physical changes

Those undergoing T therapy may notice:

  • thicker, oilier skin and larger pores
  • acne, which may peak within the first year but then improve
  • a more masculine facial appearance
  • the growth of facial hair
  • a deepening voice
  • hair growth on the arms, back, and chest
  • thinning hair on the head
  • a reduction in fat around the hips and thighs
  • an increase in stomach fat
  • increased muscle in the arms and legs
  • more prominent veins
  • an increase in sweat production
  • changes in the odors of sweat and urine

Some research also indicates that structural changes occur in the brains of those receiving continuous, high dose hormone therapy.

These changes could affect how a person interacts with others or their verbal and spatial abilities, for example.

Reproductive changes

T therapy will cause changes to the reproductive system, including:

  • menstrual changes, such as lighter, shorter, or heavier periods before they stop completely
  • difficulty releasing eggs from the ovaries
  • a reduction in the ability to get pregnant

Emotional changes

Undergoing T therapy may lead to changes in a person’s emotional state. For example, a person may experience emotional shifts, or they may feel fewer emotions than they did previously. These changes may affect how the person relates to others or how they perceive things they once enjoyed.

When a person receives treatment for gender dysphoria, they may also begin to feel more like themselves and more comfortable in their own body. Some of these changes may settle down over time.

Sexual changes

T therapy will typically change a person’s libido as well as their genitals. Individuals may experience:

  • an enlarged clitoris
  • changes in orgasms
  • changes in arousal
  • changes in sexual interests and attractions

T therapy may reduce gender dysphoria and improve mood and quality of life. It may also allow a person to experience gender congruence, which can feel empowering and liberating.

Some research indicates that T therapy can bring about a number of desired effects in transgender men, including:

  • the induction of masculine physical traits
  • increased sexual desire
  • cessation of menstruation
  • reductions in gender dysphoria
  • reductions in stress, anxiety, and depression

T therapy can involve a few risks, however, including:

  • Acne: Acne is a common side effect of T therapy. It may peak during the first year of treatment before improving. Trying acne treatments and maintaining good skin care can often help people manage the condition.
  • Fertility changes: Testosterone can reduce the ability to become pregnant, but it does not eliminate the chance. People should use birth control with any sexual partners who can produce sperm to prevent unintended pregnancy. Those who may want to get pregnant in the future should speak with a doctor about their options.
  • Hair loss: Some people will experience hair thinning following T therapy. The extent to which this occurs may depend on their age and family history. Individuals can discuss treatment options for hair loss with a doctor if they so wish.
  • Risks during pregnancy: Individuals undergoing T therapy should speak with a doctor immediately if they suspect that they are pregnant. Testosterone poses a risk to the health of the fetus.

Other complications of T therapy may include:

  • abnormal levels of lipids in the blood (dyslipidemia)
  • salt retention
  • high blood pressure
  • cardiovascular disease
  • producing too many red blood cells (erythrocytosis)
  • sleep apnea
  • weight gain

Some effects are reversible once a person stops the treatment. However, some effects are unlikely to be reversible, including:

  • clitoral growth
  • facial hair growth
  • male-pattern baldness
  • voice changes

Before a person begins T therapy, a doctor will evaluate their health. They may take a complete personal and family medical history and perform a physical examination.

The doctor may also take blood tests and a pregnancy test, as well as any other age- and sex-related screenings they feel are necessary. They will discuss the potential risks associated with the treatment and discuss contraception and future fertility.

Some people may also undergo a mental health evaluation that explores their mental health, gender dysphoria, and use of alcohol and drugs.

People under 18 years of age may also see doctors with expertise in pediatric transgender health.

Some people may wish to see a mental health professional before beginning treatment to explore potential goals, challenges, and expectations of hormone therapy, as well as its effects. They may also wish to discuss the social supports available to them.

During the visits, people will receive testosterone via an injection, patch, gel, or pill.

After starting the medication, physical changes may begin within a few weeks. Others may not appear for a few months, while some may take a few years for maximum effect.

Early changes tend to include oily skin, acne, and the cessation of menstrual periods. Later changes may include changes to facial appearance, hair growth, clitoral changes, and increased muscle mass.

People will have regular checkups with a doctor during treatment to monitor their progress and check for adverse effects. Doctors will also recommend screenings, such as breast cancer and cervical screenings, based on age-appropriate recommendations.

The results of hormone therapy can vary. They depend on factors such as genetics, overall health, and the age of the person undergoing treatment.

Starting treatment in one’s 40s or 50s, for example, can bring about less dramatic changes than those that would occur in adolescents or young adults who receive T therapy.

Once a person is within the normal range of testosterone levels for men, receiving higher doses does not typically result in more dramatic effects. However, higher doses can cause complications.

T therapy is a treatment option for those who experience gender dysphoria. It causes the development of typically masculine traits, such as facial hair growth, increased muscle mass, and a deeper voice.

This treatment may improve mental health and quality of life in those who experience gender dysphoria. It does carry some risks, however. These include hair loss, fertility changes, high blood pressure, and weight gain.

Results will vary depending on several factors, including when the person begins treatment. Individuals who wish to learn more about T therapy can speak with a doctor.