Cross-sex hormone therapy (CSH) uses medications to modify a person’s secondary sex characteristics, aligning them with their self-identified gender. This medically supervised treatment is a primary component of gender-affirming care for many transgender and gender-diverse individuals. CSH uses hormones to induce physical changes resembling those experienced during puberty. This long-term commitment helps alleviate distress associated with a mismatch between gender identity and physical presentation.
Understanding Cross-Sex Hormone Therapy
Cross-sex hormone therapy is divided into feminizing and masculinizing regimens. The medical goal is to shift the body’s hormonal environment by replacing dominant hormones with those typical of the affirmed gender. This suppresses existing characteristics and promotes the development of desired ones.
Feminizing hormone therapy typically involves administering estrogen, often with an anti-androgen medication. Estrogen promotes female secondary sex characteristics, while the anti-androgen blocks testosterone effects and suppresses its production. This combination aims to achieve hormone levels within the average range for the affirmed sex.
Masculinizing hormone therapy uses testosterone preparations to raise levels into the range typically observed in cisgender men. Elevated testosterone usually suppresses ovarian estrogen production, making a separate anti-estrogen medication unnecessary. These elevated levels then drive the development of male secondary sex characteristics.
Expected Physical Transformation and Timelines
Physical changes from CSH therapy are gradual, unfolding over several years like a second puberty. The timing and extent of these changes vary based on genetics, age at initiation, and the specific hormone regimen used. Patients should expect changes to begin within months and reach maximum effect over years.
Feminizing Changes
One of the earliest effects is a softening of the skin, which may become less oily, typically beginning within three to six months. Breast development, involving glandular tissue growth, also starts within two to six months, though maximum development can take two to three years or more. Fat redistribution begins around three to six months and continues for two to five years, shifting fat away from the abdomen toward the hips, thighs, and buttocks, changing the overall body contour. Muscle mass and strength typically decrease within three to six months, reaching their maximum effect in one to two years. Body and facial hair growth slows and thins out, starting in six to twelve months and taking over three years for the maximum effect.
Masculinizing Changes
Masculinizing therapy often results in the cessation of menstruation within two to six months. Skin changes, such as increased oiliness and potential acne, are often among the first signs, appearing within one to six months. The voice deepens due to vocal cord thickening, a change that begins within three to twelve months, with the full effect taking one to two years. Facial and body hair growth, including the potential for male-pattern baldness, starts in the first three to six months, but full growth can take three to five years. Muscle mass and strength increase, with noticeable effects starting around six to twelve months and continuing for two to five years. Clitoral enlargement is an irreversible change that typically starts within three to six months and stabilizes over one to two years.
Methods of Administration
CSH hormones can be administered through several routes, depending on patient preference, desired absorption rate, and medical considerations. The most common methods include oral, injectable, and transdermal formulations.
Oral administration, typically in pill form, is a common and convenient daily option for estrogen. However, oral estrogen is metabolized by the liver, which can slightly increase the risk of venous thromboembolism (blood clots) compared to other methods. Because of concerns about liver toxicity and poor absorption, testosterone is generally not given orally in the United States.
Injections are a frequent method for both estrogen and testosterone, providing a steady release into the bloodstream. Testosterone is often administered via intramuscular or subcutaneous injections, typically weekly or bi-weekly. Estrogen injections are also an option, usually given weekly or every two weeks.
Transdermal delivery systems, such as patches, gels, or sprays applied to the skin, are available for both hormones. Transdermal estrogen is often preferred for patients with risk factors because it bypasses the liver, potentially lowering the risk of blood clots compared to oral pills. Implants, which are small pellets placed under the skin that release hormones slowly over several months, are also an option.
Medical Monitoring and Safety
CSH therapy requires consistent medical oversight to ensure efficacy and patient safety. Regular blood tests monitor hormone levels, confirming they are within the desired physiological range for the affirmed sex. These tests also check for potential metabolic changes that could indicate health concerns.
Monitoring Feminizing Therapy
Monitoring focuses on liver function, lipid panels, and potassium levels, especially when anti-androgens like spironolactone are used. Estrogen carries an increased risk of venous thromboembolism (blood clots). For this reason, non-oral formulations are often recommended for those with existing risk factors. Transgender women may also have an elevated cardiovascular risk that requires careful management of blood pressure and cholesterol levels.
Monitoring Masculinizing Therapy
Blood monitoring includes checking hematocrit and hemoglobin levels. Testosterone can cause erythrocytosis, which is an increase in red blood cells. Elevated red blood cell counts can thicken the blood and increase the risk of complications, necessitating a dose adjustment if levels become too high. Testosterone may also affect lipid profiles, potentially increasing LDL cholesterol and triglycerides.
All patients undergoing CSH therapy should discuss long-term health considerations with their provider before beginning treatment. These discussions often include the potential impact on fertility, making fertility preservation options a consideration for many individuals. Bone density should also be monitored regularly, as maintaining sex hormone levels within the appropriate physiological range is important for long-term bone health.