Trans men can achieve adequate muscular development through low-dose testosterone therapy: A long-term study on body composition changes.

Both low-dose and high-dose testosterone groups showed decreases in body fat percentage and increases in lean body mass during the first year of therapy, followed by a slight increase in both over the long term.

• Low-dose group was defined as ≤62.5 mg/wk and high-dose group as >62.5 mg/wk of testosterone
• Of 291 participants, 188 patients (64.6%) were in the low-dose group and 103 (35.4%) in the high-dose group
• Both groups demonstrated the same directional changes in body fat percentage and lean body mass during the first year
• After the first year, both body fat percentage and lean body mass showed a slight increase over the long term in both groups

The high-dose testosterone group exhibited greater lean body mass gains during the first year of therapy compared to the low-dose group.

• Higher hormone doses were associated with lean body mass increases at 3 months (P = 0.006) and 6 months (P = 0.015)
• Lower initial lean body mass values were also associated with lean body mass increases at 3 months (P < 0.001) and 6 months (P < 0.001)
• The difference in lean body mass gains between groups was most pronounced during the first year of treatment
• Despite greater early gains, the low-dose group still achieved adequate muscular development over the long term

Cumulative menstrual cessation rates up to 12 months were not significantly different between the low-dose and high-dose testosterone groups.

• Menstrual cessation was one of the recorded physical findings alongside body mass index, body fat percentage, lean body mass, and grip strength
• No statistically significant difference was found between groups in cumulative menstrual cessation rates within the first 12 months
• The study period for participant initiation of gender-affirming hormone therapy spanned from May 2000 to December 2021

There were no long-term, dose-dependent side effects such as polycythemia or dyslipidemia observed in either testosterone dose group.

• Blood testing results monitored included hemoglobin, hematocrit, uric acid, creatinine, total cholesterol, triglycerides, and total testosterone
• Polycythemia and dyslipidemia were specifically assessed as potential adverse effects of testosterone therapy
• No dose-dependent relationship was found for these safety parameters over the long-term follow-up period
• The study was a retrospective analysis spanning participants who initiated therapy between May 2000 and December 2021

Low-dose testosterone administration (≤62.5 mg/wk) is sufficient to increase lean body mass in trans men.

• The majority of the study cohort (188 of 291 patients, 64.6%) were in the low-dose group
• Low-dose group still demonstrated measurable increases in lean body mass, particularly during the first year
• The authors concluded that while higher doses lead to earlier muscle mass increases, low-dose therapy achieves adequate muscular development
• This finding supports the use of lower testosterone doses as an effective option for gender-affirming hormone therapy in trans men

Few long-term studies on the safety and efficacy of gender-affirming hormone therapy were available prior to this study.

• The paper identifies a gap in the literature regarding long-term safety and efficacy data for testosterone therapy in trans men
• The study was designed specifically to investigate long-term physical effects and safety of testosterone therapy
• The retrospective analysis included 291 trans men who initiated gender-affirming hormone therapy over a 21-year period (May 2000 to December 2021)