Abstract Body: Transgender females (TGF) are individuals born biologically male, but identify as female. Gender-Affirming Hormone Therapy (GAHT) consists of 17β-Estradiol (E2) supplementation with androgen suppression or a surgical intervention in order to match physical characteristics with perceived gender. Whether the prevalence of cardiovascular (CV) disease is enhanced in TGFs on GAHT is not clear. We previously reported that baseline cardiac morphology and function is not altered in a rat model of cross sex hormone therapy (CSHT) that mimics GAHT in the TGF. This study tested the hypothesis that myocardial ischemia will result in enhanced cardiac susceptibility in the male rat on CSHT. Adult male Sprague Dawley rats (13 weeks of age) were randomly assigned to either Control or E2+CTX; E2 at 5 mg/day, pellet sc, replaced every 3 weeks with castration (CTX) performed at 15 weeks of age. At 25 weeks of age, rats in each group were randomly subdivided into Sham (n=8) or myocardial ischemia/reperfusion (MIR), 1 hour occlusion, n=6-7. Statistics: Two-way ANOVA with Tukey’s post-hoc test. *Denotes significance vs. Control Sham. Results (Table): At 27 weeks of age, total lean mass (EchoMRI) was significantly decreased in Sham and I/R E2+CTX (p<0.05). At one week post I/R, stroke volume and cardiac output (echocardiogram, VEVO 3100) were significantly decreased in E2+CTX Sham vs. Control Sham (p<0.05); yet, ejection fraction, end-diastolic volume, and end-systolic volume did not differ. Thus, these data suggest that the biological effects of CSHT in the male does not enhance susceptibility to cardiac ischemia in young adulthood; yet, the long-term effect of CSHT on CV health remains unknown.