Purpose <p>to describe 10-year changes in health measures and cardiovascular risk among transmasculine adults on testosterone-based Gender-Affirming Hormone Therapy.</p> Methods <p>this is a single-centre, longitudinal cohort study of transmasculine adults who began Gender-Affirming Hormone Therapy and were followed-up for a total of 10 years according to standard clinical practice, which includes yearly visits with complete physical examinations, blood tests, and assessment of body composition. For participants aged 35 years or older, we estimated the 10-year cardiovascular risk, and then compared it with age-matched people from the general population.</p> Results <p>57 participants completed 10 years of follow-up. Nearly half smoked and few were physically active. Haemoglobin and haematocrit rose early and then stabilised within usual ranges; very high values were uncommon. Fasting glucose, insulin, and blood pressure did not change meaningfully. The lipid profile worsened: LDL, total cholesterol and triglycerides increased, and HDL decreased throughout the study period. Weight, body mass index, waist circumference, and waist-to-hip ratio increased. Body composition showed higher lean mass and trunk fat, with a shift toward android fat distribution. No major cardiovascular events were recorded. One participant developed atrial fibrillation. Metabolic syndrome by female criteria became more frequent. cardiovascular risk was higher than cisgender women but similar to cisgender men at ages 35–44; at ages 45–54 it was lower than cisgender men.</p> Conclusions <p>Over 10 years, testosterone-based Gender-Affirming Hormone Therapy is linked to less favorable lipid profiles and body composition patterns, supporting constant monitoring, risk-factor treatment, and lifestyle support.</p>