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

Yusuke Tominaga; Tomoko Kobayashi; Yuko Matsumoto; Takatoshi Moriwake; Yoshitaka Oshima; Misa Okumura; Satoshi Horii; Takuya Sadahira; Satoshi Katayama; Takehiro Iwata; Shingo Nishimura; Kensuke Bekku; Kohei Edamura; Morito Sugimoto; Yasuyuki Kobayashi; Masami Watanabe; Yuzaburo Namba; Yosuke Matsumoto; Mikiya Nakatsuka; Motoo Araki

doi:10.1111/andr.13640

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

Andrology. 2024 Apr 2. doi: 10.1111/andr.13640. Online ahead of print.

Authors

Yusuke Tominaga¹, Tomoko Kobayashi¹, Yuko Matsumoto², Takatoshi Moriwake¹, Yoshitaka Oshima³, Misa Okumura¹, Satoshi Horii¹, Takuya Sadahira¹, Satoshi Katayama¹, Takehiro Iwata¹, Shingo Nishimura¹, Kensuke Bekku¹, Kohei Edamura¹, Morito Sugimoto⁴, Yasuyuki Kobayashi¹, Masami Watanabe⁵, Yuzaburo Namba⁶, Yosuke Matsumoto⁶, Mikiya Nakatsuka⁷, Motoo Araki¹

Affiliations

¹ Department of Urology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
² Department of Urology, Good Life Hospital, Hiroshima, Japan.
³ Department of Neuropsychiatry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
⁴ Department of Urology, Onomichi Municipal Hospital, Hiroshima, Japan.
⁵ Center for Innovative Clinical Medicine, Okayama University Graduate School of Medicine, Okayama, Japan.
⁶ Gender Center, Okayama University Hospital, Okayama, Japan.
⁷ Faculty of Health Sciences, Okayama University Graduate School of Medicine, Okayama, Japan.

PMID: 38563871
DOI: 10.1111/andr.13640

Abstract

Background: Transgender individuals undergo the gender-affirming hormone therapy (GAHT) to achieve physical changes consistent with their gender identity. Few studies are available on the long-term safety and efficacy of GAHT.

Objectives: To investigate the long-term physical effects and the safety of the testosterone therapy for trans men and to assess the impact of differential hormone dose.

Materials and methods: Trans men who initiated GAHT between May 2000 and December 2021 were included in this retrospective analysis. Physical findings (body mass index, body fat percentage (BFP), lean body mass (LBM), and grip strength), blood testing results (hemoglobin, hematocrit, uric acid, creatinine, total cholesterol, triglycerides, and total testosterone), and menstrual cessation were recorded. We assessed the effects of testosterone on body composition changes and laboratory parameters, comparing a low-dose group (≤ 62.5 mg/wk) to a high-dose group (> 62.5 mg/wk).

Results: Of 291 participants, 188 patients (64.6%) were in the low-dose group and 103 (35.4%) in the high-dose group. Cumulative menstrual cessation rates up to 12 months were not significantly different between groups. Both groups showed a decrease in BFP and an increase in LBM during the first year of therapy, followed by a slight increase in both over the long term. The high-dose group exhibited greater LBM gains during the first year. Higher hormone doses and lower initial LBM values were associated with LBM increases at 3 and 6 months (3 mo, P = 0.006, P < 0.001; 6 mo, P = 0.015, P < 0.001). There were no long-term, dose-dependent side effects such as polycythemia or dyslipidemia.

Conclusion: Long-term GAHT for trans men is safe and effective. Low-dose testosterone administration is sufficient to increase LBM in trans men. Higher testosterone doses can lead to an earlier increase in muscle mass.

Keywords: body composition; hormone therapy; lean body mass; testosterone; transgender.