Masculinizing hormone therapy is used to induce the physical changes in your body caused by male hormones during puberty (secondary sex characteristics) to promote the matching of your gender identity and body (gender congruence). If masculinizing hormone therapy is started before the changes of female puberty begins, female secondary sex characteristics, such as the development of breasts, can be avoided. Masculinizing hormone therapy is also known as gender-affirming hormone therapy.

During masculinizing hormone therapy, you'll be given the male hormone testosterone, which suppresses your menstrual cycles and decreases the production of estrogen from your ovaries. Changes caused by these medications can be temporary or permanent. Masculinizing hormone therapy can be done alone or in combination with masculinizing surgery.

Masculinizing hormone therapy isn't for all transgender men, however. Masculinizing hormone therapy can affect your fertility and sexual function and cause other health problems. Your doctor can help you weigh the risks and benefits.

Masculinizing hormone therapy is used to alter your hormone levels to match your gender identity.

Typically, people who seek masculinizing hormone therapy experience discomfort or distress because their gender identity differs from their sex assigned at birth or from their sex-related physical characteristics (gender dysphoria). To avoid excess risk, the goal is to maintain hormone levels in the reference range for the target gender.

Masculinizing hormone therapy can:

• Make gender dysphoria less severe
• Reduce psychological and emotional distress
• Improve psychological and social functioning
• Improve sexual satisfaction
• Improve quality of life

Research suggests that masculinizing hormone therapy can be safe and effective.

If used in an adolescent, hormone therapy typically begins at age 16. Ideally, treatment starts before the development of secondary sex characteristics so that teens can go through puberty as their identified gender. Gender affirming hormone therapy is not typically used in children.

Masculinizing hormone therapy isn't for everyone, however. Your doctor might discourage masculinizing hormone therapy if you:

• Had or have a hormone-sensitive cancer, such as breast cancer
• Have a thromboembolic disease, such as when a blood clot forms in one or more of the deep veins of your body (deep vein thrombosis) or a blockage in one of the pulmonary arteries in your lungs (pulmonary embolism)
• Are pregnant or breastfeeding
• Have uncontrolled behavioral health conditions
• Have uncontrolled significant medical conditions
• Have a condition that limits your ability to provide informed consent

Talk to your doctor about the changes in your body and any concerns you might have. Complications of masculinizing hormone therapy include:

• Producing too many red blood cells (polycythemia)
• Weight gain
• Acne
• Developing male-pattern baldness
• Sleep apnea
• Developing an abnormal level of cholesterol and other lipids, which may increase cardiovascular risk (dyslipidemia)
• High blood pressure (hypertension)
• Type 2 diabetes
• Deep vein thrombosis and/or pulmonary embolism (venous thromboembolism)
• Infertility
• A condition where the lining of the vagina becomes drier and thinner (atrophic vaginitis)
• Pelvic pain
• Clitoral discomfort

Evidence suggests that transgender men have no increased risk of breast cancer or cardiovascular disease when compared to women whose gender identity and expression matches the stereotypical societal characteristics related to their sex assigned at birth (cisgender women).

Conclusions can’t be drawn about whether masculinizing hormone therapy increases the risk of ovarian and uterine cancer. Further research is needed.

Your fertility

Because masculinizing hormone therapy might reduce your fertility, you'll need to make decisions about your fertility before starting treatment. The risk of permanent infertility increases with long-term use of hormones, especially when hormone therapy is initiated before puberty. Even after stopping hormone therapy, ovarian and uterine function might not recover well enough to ensure that you can become pregnant without reproductive technology assistance.

If you want to have biological children, talk to your doctor about egg freezing (mature oocyte cryopreservation) or embryo freezing (embryo cryopreservation). Another option involves having ovarian tissue surgically removed, frozen and later thawed and reimplanted (ovarian tissue cryopreservation). Keep in mind that egg freezing has multiple steps — ovulation induction, egg retrieval and freezing. If you want to freeze embryos, you'll need to go through the additional step of having your eggs fertilized before they are frozen.

At the same time, while testosterone might limit your fertility, you're still at risk of pregnancy if you have your uterus and ovaries. If you want to avoid becoming pregnant, use an intrauterine device, a barrier form of contraception or a continuous progestin form of birth control.

Before starting masculinizing hormone therapy, your doctor will evaluate your health to rule out or address any medical conditions that might affect or contraindicate treatment. The evaluation might include:

• A review of your personal and family medical history
• A physical exam, including an assessment of your external reproductive organs
• Lab tests measuring your lipids, blood sugar, blood count, liver enzymes and electrolytes, and a pregnancy test
• A review of your immunizations
• Age- and sex-appropriate screenings
• Identification and management of tobacco use, drug abuse, alcohol abuse, HIV and other sexually transmitted infections
• Discussion about contraception and your desire for future fertility
• Discussion about use of potentially harmful treatment approaches, such as unprescribed hormones or industrial-strength silicone injections

You might also need a behavioral health evaluation by a provider with expertise in transgender health. The evaluation might assess:

• Your gender identity and gender dysphoria
• The impact of your gender identity at work, school, home and social environments, including issues related to discrimination, relationship abuse and minority stress
• Mood or other mental health concerns
• Sexual health concerns
• Risk-taking behaviors, including substance use and use of nonmedical-grade silicon injections or unapproved hormone therapy or supplements
• Protective factors such as social support from family, friends and peers
• Your goals, risks and expectations of treatment and your future care plans

Adolescents younger than age 18, accompanied by their custodial parents or guardians, also should see doctors and behavioral health providers with expertise in pediatric transgender health to discuss the risks of hormone therapy, as well as the impact and possible complications of gender transition in that age group.

During the procedure

You'll begin masculinizing hormone therapy by taking testosterone. Typically, your doctor will prescribe a low dose and slowly increase the dosage over a period of months. Testosterone is given either by injection or a gel applied to the skin. Other testosterone preparations can be used, such as a patch or pellets placed under the skin. In the U.S., testosterone also can be given as a long lasting injection or as twice daily pills (testosterone undecanoate). Oral methyltestosterone or synthetic male sex hormone (androgen) medication shouldn't be used because of potential harmful effects on your liver and lipids.

If you have persistent menstrual flow, your doctor might recommend taking progesterone to control it.

Masculinizing hormone therapy will begin producing changes in your body within weeks to months. Your timeline might look as follows:

• Stopping your period. This will occur within two to six months of treatment.
• Voice deepening. This will begin three to 12 months after treatment. The maximum effect will occur within one to two years.
• Facial and body hair growth. This will begin three to six months after treatment. The maximum effect will occur within three to five years.
• Body fat redistribution. This will begin within three to six months. The maximum effect will occur within two to five years.
• Clitoral enlargement and vaginal atrophy. This will begin three to twelve months after treatment. The maximum effect will occur within one to two years.
• Increased muscle mass and strength. This will begin within six to 12 months after treatment. The maximum effect will occur within two to five years.

While on masculinizing hormone therapy, you'll meet regularly with your doctor. He or she will:

• Document your physical changes
• Monitor your hormone concentration, and use the lowest dose necessary to achieve desired physical effects
• Monitor changes in your lipids, fasting blood sugar, blood count, liver enzymes and electrolytes that could be caused by hormone therapy
• Monitor your behavioral health

You will also need routine preventive care if you haven’t had certain surgical interventions, including:

• Breast cancer screening. This should be done according to age-appropriate breast cancer screening recommendations for cisgender women. If mammography isn’t possible due to masculinizing chest surgery, breast self-exams are recommended.
• Cervical cancer screening. This should be done according to age-appropriate cervical cancer screening recommendations for cisgender women. Be sure the pathologist knows that you’re on testosterone therapy. This therapy can cause your cervical tissues to thin (cervical atrophy), which might mimic a condition in which abnormal cells are found on the surface of the cervix (cervical dysplasia).
• Evaluation of vaginal bleeding. If you have persistent or recurrent vaginal bleeding, early evaluation is important.
• Supplementation. This includes standard calcium and vitamin D supplementation, along with bone density assessment according to the age-appropriate recommendations for cisgender men.