Age-Dependent Muscular Response to Testosterone-Based Gender-Affirming Therapy: Evidence From a 1-Year Observational Study
Authors' conclusion
Age at GAHT initiation markedly influences the anabolic response to testosterone therapy. Strength gains are more pronounced in early adulthood and decline with age, information that may assist clinicians in providing age-appropriate counseling for individuals beginning testosterone therapy.
Study context
- Population
- Transgender and gender-diverse adults assigned female at birth, naïve to gender-affirming hormone therapy (GAHT) and gender-affirming surgeries, starting testosterone therapy
- Participants
- 107 participants
- Exposure
- 1-year changes after testosterone-based GAHT across baseline age groups
- Outcome
- Changes in muscle strength (handgrip strength) and mass (DXA body composition), and whether they differ by age at treatment onset
- Follow-up
- 12 months
Methodological detailsage-stratified (20-24, 25-29, 30-34, ≥35 years)
- Age-stratified (20-24, 25-29, 30-34, ≥35 years)
Main finding
As reported in the abstract
Change in handgrip strength · 1 year
| Group | Value | P |
|---|---|---|
| 20-24 | +2.14 kg | P = .025 |
| 25-29 | +4.35 kg | P = .001 |
Value
20-24+2.14 kg
25-29+4.35 kg
P
20-24P = .025
25-29P = .001
Observational data: associations, not effects.
Further findings
Appendicular skeletal muscle mass index · 1 year
- Modest, non-significant increases in younger participants; plateaued or declined from age 30 onward, with the 30-34 group showing a decline most evident at the 25th percentile
Original publication
Age-Dependent Muscular Response to Testosterone-Based Gender-Affirming Therapy: Evidence From a 1-Year Observational Study. Endocr Pract. Published 17 December 2025. doi:10.
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