Cross Sex Steroid Therapy and Baseline Cardiac Function in a Rodent Model of Gender Affrming Hormone Therapy in the Male Rat

Transgender females (TGF) are individuals who are born biologically male, but identify as female. Gender-Affrming Hormone Therapy (GAHT), consisting of 17β-Estradiol (E2) supplementation with androgen suppression i.e. castration (CTX), is used in TGFs to match their physical characteristics with their perceived gender. Previously, we reported that E2+CTX in the normotensive male Sprague-Dawley (SD) rat is associated with a significant increase in E2 and decrease in testosterone, body weight, and lean mass. Whether GAHT enhances cardiac morbidity and mortality in the transgender population on GAHT relative to cisgender individuals is still unclear. Moreover, the sustained effect of high E2 coupled to androgen suppression in male rats on their cardiac morphology and function is unknown. Thus, this study tested the hypothesis that GAHT in the adult male SD rat is associated with impaired cardiac function under baseline conditions. Methods: Adult male SDs (13 weeks of age) were randomly assigned to either: Control or E2+CTX therapy (E2 at 5 mg/day, pellet sc, replaced every 3 weeks, with CTX performed at 15 weeks of age) (n=8/grp). Baseline cardiac function was measured via echocardiogram (VEVO 3100), body composition via EchoMRI. Results: at 28 weeks of age, total lean mass and body weight were significantly decreased in the E2+CTX group, as previously observed; total fat mass did not differ between groups. Heart rate was significantly decreased; yet, other indices of cardiac function were not altered at baseline. Although no major differences in baseline cardiac function were observed, the long-term impact of GAHT on CV health and the ability of the heart to respond to secondary challenges are unknown. This study is ongoing and further studies will determine the ability of the heart to recover from secondary insults in order to determine if GAHT in males is associated with increased CV risk. Formula: see text Funding sources: HL143459, P20-GM-104357, P20-GM121334, T32-HL105324. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.