Longitudinal data over 5-6 years show that gender-affirming hormone therapy produces body composition changes that move almost completely toward the affirmed sex phenotype, but also reveal cardiometabolic risk changes—particularly increased visceral fat, triglycerides, and LDL cholesterol in transgender men—underscoring the importance of continued clinical monitoring.
Key Findings
Results
Skeletal muscle size increased in transgender men and decreased in transgender women over the follow-up period.
Transgender men (TM; n=17, mean age 25±5 years) showed a 21% increase in skeletal muscle size after 6 years of hormone therapy.
Transgender women (TW; n=16, mean age 28±5 years) showed a 7% decrease in skeletal muscle size after 5 years of hormone therapy.
Whole-body and regional muscle volumes were analyzed using magnetic resonance imaging.
Study used a longitudinal prospective cohort design with measurements at baseline, 1 year, and 5-6 years.
Results
Muscle strength increased significantly in transgender men but was statistically unchanged in transgender women.
Muscle strength increased 18% after 6 years in TM (p=0.003).
Muscle strength was statistically unchanged in TW after 5 years of hormone therapy.
These findings follow the expected direction of the affirmed sex phenotype for both groups.
Results
Muscle fat infiltration changed almost completely toward the affirmed sex phenotype after just 1 year of hormone therapy in both transgender men and transgender women.
The change in muscle fat infiltration was statistically significant (p<0.05) in both TM and TW.
This shift toward affirmed sex phenotype occurred rapidly, within 1 year of initiating hormone therapy.
Muscle fat infiltration was assessed using magnetic resonance imaging.
Results
Transgender women increased total adiposity but decreased visceral fat volume, while transgender men showed increased visceral fat and liver fat with relatively stable total adipose tissue levels.
TM showed a 70% increase in visceral fat volume over the follow-up period.
TM also showed increased liver fat content.
TW demonstrated increased total adiposity alongside a decrease in visceral fat volume.
TM had relatively stable total adipose tissue levels despite large increases in visceral fat.
Fat volumes were measured using whole-body magnetic resonance imaging.
Results
Transgender men showed significant worsening of lipid cardiometabolic biomarkers after 6 years of hormone therapy.
There was a significant increase in triglyceride levels in TM after 6 years.
LDL cholesterol levels significantly increased in TM after 6 years.
HDL cholesterol levels significantly decreased in TM after 6 years.
These lipid changes suggest increased cardiometabolic risk in TM on long-term hormone therapy.
Blood samples were taken at baseline, 1 year, and 5-6 years for biomarker analysis.
Results
Arterial stiffness and blood pressure did not change significantly in either transgender men or transgender women over the follow-up period.
Neither TM nor TW showed significant changes in arterial stiffness over 5-6 years of hormone therapy.
Blood pressure remained statistically unchanged in both groups.
These findings contrast with the adverse lipid profile changes observed in TM.
Background
Longitudinal studies on hormone therapy in transgender individuals are rare and typically limited to short follow-up periods.
The authors note that longitudinal studies in this population are rare and often limited to 1- to 2-year follow-up periods.
This study provides measurements at baseline, 1 year, and 5-6 years, representing a longer follow-up than most prior studies.
The sample included TM (n=17) and TW (n=16) in a prospective cohort design.
Lundberg T, Tryfonos A, Eriksson L, Rundqvist H, Rullman E, Holmberg M, et al.. (2025). Longitudinal changes in regional fat and muscle composition and cardiometabolic biomarkers over 5 years of hormone therapy in transgender individuals.. Journal of internal medicine. https://doi.org/10.1111/joim.20039