Gender-Affirming Hormone Therapy: Personalized Approaches to Supporting Physiological Transition

Understanding Hormones in Gender-Affirming Care

Hormones act as essential regulators of human physiology, influencing secondary sex characteristics, body composition, metabolism, reproductive function, mood, and overall health. In gender-affirming care, hormone therapy is used to help align an individual’s physical characteristics with their gender identity by modifying endogenous hormone signaling.

Gender-affirming hormone therapy (GAHT) involves the use of sex hormones—including estrogen, testosterone, and medications that influence endogenous hormone activity to promote desired physiological changes. Treatment is individualized based on each person’s goals, health history, age, baseline hormone levels, and desired degree of physical change. 

Unlike hormone replacement therapies used for menopause or hypogonadism, GAHT is not primarily intended to correct hormone deficiency. Instead, it uses carefully managed hormone exposure to guide the development or suppression of sex-associated characteristics. 

As understanding of transgender health continues to advance, hormone therapy has become an important component of gender-affirming care. Modern approaches focus on personalized treatment strategies that prioritize safety, appropriate monitoring, and patient-specific goals. 

The Science Behind Gender-Affirming Hormone Therapy 

Sex hormones influence tissues throughout the body by interacting with specific hormone receptors and regulating cellular activity. Estrogen primarily acts through estrogen receptors (ERα and ERβ), while testosterone influences androgen receptors expressed in tissues including muscle, bone, skin, cardiovascular tissue, and reproductive organs. 

By changing the balance of circulating sex hormones, GAHT can influence: 

•  Body composition and fat distribution
• Muscle mass and strength
• Skin characteristics
• Hair growth patterns
• Breast development
• Voice-related changes
• Sexual function
• Bone health
• Mood and emotional well-being

The timing, degree, and permanence of changes vary significantly between individuals. Factors such as genetics, age at treatment initiation, baseline hormone levels, and duration of therapy all contribute to treatment outcomes. 

Because hormone response differs between individuals, effective GAHT requires ongoing assessment and personalized adjustment rather than a standardized approach. 

Feminizing Hormone Therapy 

Feminizing hormone therapy is commonly used by transgender women and transfeminine individuals to promote feminine physical characteristics while reducing the effects of endogenous testosterone. 

Estrogen Therapy 

Estradiol is the primary hormone used in feminizing HRT. As the biologically active form of estrogen, estradiol interacts with estrogen receptors throughout the body to influence tissues involved in breast development, skin structure, fat distribution, and reproductive physiology. 

Feminizing HRT may contribute to: 

• Breast development
• Redistribution of body fat toward a typically feminine pattern
• Softer skin texture due to changes in skin structure and oil production
• Reduced muscle mass over time
• Changes in libido and sexual function 

Testosterone Suppression 

Because testosterone promotes many masculinizing characteristics, some individuals may use medications that reduce androgen production or block androgen activity. 

Reducing androgen signaling may support changes such as:

• Reduced body and facial hair growth
• Decreased testosterone-driven skin changes
• Reduced muscle maintenance
• Further alignment with desired physical characteristics 

The combination of estrogen therapy and testosterone suppression is individualized based on treatment goals, hormone levels, response, and overall health considerations.

Masculinizing Hormone Therapy 

Masculinizing hormone therapy is commonly used by transgender men and transmasculine individuals to promote masculine physical characteristics through testosterone therapy. 

Testosterone acts primarily through androgen receptors throughout the body, influencing muscle tissue, hair follicles, vocal structures, metabolism, and reproductive tissues. 

Masculinizing HRT may contribute to:

• Increased muscle mass and strength
• Redistribution of body fat toward a typically masculine pattern
• Increased facial and body hair growth
• Deepening of the voice
• Increased skin oil production
• Changes in libido and sexual function
• Suppression of menstruation 

Unlike feminizing therapy, testosterone is typically the primary medication used. Treatment plans may still vary depending on individual goals, health factors, and response to therapy.

Because testosterone influences multiple physiological systems, monitoring remains an important component of long-term care. 

Feminizing vs. Masculinizing HRT: Understanding the Differences 

Although both feminizing and masculinizing hormone therapies use sex hormones to promote physical changes aligned with an individual’s gender identity, they work through different biological pathways and treatment strategies. 

Feminizing Hormone Therapy 

Feminizing HRT focuses on increasing estrogen signaling while reducing the effects of endogenous androgens such as testosterone. 

The primary hormone used is estradiol, which influences estrogen-responsive tissues throughout the body. Additional medications may be used to reduce androgen activity depending on individual treatment goals. 

Common changes associated with feminizing HRT include: 

• Breast development
• Increased feminine fat distribution patterns
• Softer skin characteristics
• Reduced muscle mass over time  
• Decreased androgen-associated features 

Monitoring typically includes assessment of hormone levels, cardiovascular health, bone health, and overall treatment response. 

Masculinizing Hormone Therapy 

Masculinizing HRT focuses on increasing androgen signaling through testosterone therapy. 

Testosterone influences tissues involved in muscle development, hair growth, vocal changes, and body composition. 

Common changes associated with masculinizing HRT include: 

• Increased muscle mass
• Facial and body hair growth 
• Voice deepening
• Changes in fat distribution
• Increased skin oil production
• Menstrual suppression 

Monitoring commonly includes testosterone levels, red blood cell production, metabolic health markers, and long-term cardiovascular and bone health.

The Role of Compounded Hormone Therapy in Gender-Affirming Care 

Compounding may allow for: 

• Customized hormone concentrations
• Alternative dosage forms, including transdermal creams and gels
• Preservative-free or dye-free formulations
• Individualized combinations of hormones based on patient-specific needs 

For gender-affirming care, compounded formulations may provide additional options for individuals who require specific dosing adjustments, have sensitivities to certain excipients, or prefer alternative delivery approaches. 

Common bioidentical hormone preparations used in compounded hormone therapy may include estradiol, estriol, progesterone, DHEA, and testosterone. Depending on clinical goals, compounded estrogen formulations may also incorporate combinations such as Bi-Est (estradiol and estriol) or Tri-Est (estrone, estradiol, and estriol), while progesterone-containing formulations may be used when clinically appropriate. 

The effectiveness of compounded therapy depends not only on the active hormone but also on the quality of the delivery system. The compounding base plays an important role in supporting hormone incorporation, formulation stability, skin tolerability, and patient experience. 

Advancing Transdermal Hormone Delivery Through Formulation Science 

Transdermal hormone delivery provides an important alternative route for administering hormones by allowing absorption through the skin and providing a convenient, non-invasive approach for many patients. 

The design of the transdermal base is a critical factor in supporting consistent formulation performance. An effective compounding vehicle must balance hormone compatibility, stability, skin tolerability, and delivery characteristics while allowing pharmacists to prepare individualized formulations.