(136) Testosterone Effects on Flow-Mediated Dilatation Among Hormone-Naïve Transmasculine Individuals

Introduction Transmasculine individuals (TM) undergoing testosterone therapy may experience cardiometabolic effects, but data on its impact on endothelial function is still lacking. Endothelial dysfunction, indicated by imbalances in vasodilation and vasoconstriction is one of the most critical factors in cardiovascular disease development. While testosterone therapy is essential for masculinization in TM, understanding its cardiovascular effects is vital for prudential monitoring, counseling and screening in this population. Objective The primary objective was to assess the effect testosterone therapy on endothelial function among hormone-naïve TM by comparing flow-mediated dilation (FMD) at baseline and 12 weeks after initiation. Secondary objectives were to compare blood pressure, body mass index (BMI), lipid profile, and hemoglobin/hematocrit (Hb/Hct) levels between baseline and 12 weeks after testosterone therapy. Methods This prospective study was conducted at the Gender Health Clinic, King Chulalongkorn Memorial Hospital from January to August 2024. Hormone-naïve Thai TM aged 18-40 were recruited. Participants received testosterone enanthate 250 milligrams intramuscularly every 3 weeks for 12 weeks. FMD measurement by B-mode ultrasound at brachial artery were assessed at baseline and 12 weeks after therapy. Cardiometabolic parameters (blood pressure, BMI, lipid profile, Hb/Hct) were also assessed at baseline and 12 weeks after therapy. Results A total of 25 TM were recruited with mean age of 28.0 ± 6.1 years. After 12 weeks of testosterone therapy, FMD (%) showed no significantly different compared to baseline, 7.65 (5.74–11.23) versus 7.24 (5.64–9.78), p=0.128. BMI was significantly higher at 12 weeks after therapy, 24.4 ± 4.1 versus 22.9 ± 3.9 kg/m2, p < 0.001. Hematocrit levels (%) significantly increased at 12 weeks after therapy, 42.4 ± 2.8 versus 39.9 ± 2.3, p < 0.001. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) demonstrated no statistically significant different compared to baseline. HDL levels decreased significantly from 59.2 ± 11.2 to 51.0 ± 11.2 mg/dL, p < 0.001, while LDL and triglyceride levels demonstrated no significant changes, p=0.26 and 0.57, respectively. Conclusions Hormone-naïve transmasculine individuals showed no significant changes in endothelial function, as measured by FMD after 12 weeks of testosterone therapy. However, significant increases in BMI and reductions in HDL cholesterol were observed. Cardiovascular disease is complex and influenced by multiple factors, including metabolic parameters, genetics, physical activities, sex hormones, and other risk factors. This study focused primarily on a short-period of endothelial function assessment after testosterone therapy while cardiovascular function involved by multiple parameters. Further research is needed to assess the long-term impacts of testosterone therapy on endothelial function and cardiovascular health in this population. Disclosure No