Body composition and cardiometabolic changes during gender-affirming hormone therapy: 12-month longitudinal study

Background Testosterone therapy induces well-known changes in body composition in transgender men; however, its short-term cardiometabolic effects remain incompletely characterized. This study aimed to evaluate body composition and cardiometabolic changes during testosterone therapy over a 12-month period.Methods This retrospective observational study included 15 transgender men initiating intramuscular testosterone therapy who were followed for 12 months. Anthropometric measurements, body composition, blood pressure, and laboratory parameters including lipid profile, fasting glucose, HbA1c, plasma atherogenic index (PAI), and triglyceride–glucose (TyG) index were assessed at baseline and at 12 months. All participants initiated intramuscular depot testosterone therapy administered every 28 days. None of the participants underwent oophorectomy during the study period.Results Total testosterone levels increased significantly from 40.82 ± 19.46 ng/dL to 338.06 ± 205.02 ng/dL (p < 0.001), while estradiol levels remained stable. Systolic blood pressure and mean arterial pressure showed mild but non-significant increases during follow-up. Body weight, body mass index, and fat-free mass increased significantly, while body fat percentage decreased. HDL cholesterol levels decreased (59.7 ± 11.2 to 52.3 ± 13.2 mg/dL, p = 0.019), and triglyceride levels showed a non-significant upward trend. The PAI increased from 0.08 ± 0.24 to 0.23 ± 0.25 (p = 0.017), and the TyG index rose from 8.02 ± 0.43 to 8.21 ± 0.39 (p = 0.016). Blood pressure parameters did not change significantly.Conclusions In transgender men without oophorectomy, testosterone therapy was associated with favorable changes in body composition alongside modest shifts in cardiometabolic indices over a 12-month period. These findings suggest that simple indices such as PAI and TyG may be useful for monitoring early cardiometabolic changes attributable to exogenous testosterone therapy. Larger prospective studies are warranted to confirm these observations.