Gender-affirming hormone therapy and its impact on myocardial mass and cardiac function: a prospective magnetic resonance cohort study on transgender men and women

Objective: Differences in cardiac parameters such as myocardial mass, left ventricular ejection fraction (LVEF), cardiac output, and brain natriuretic peptide (NT-proBNP) levels between cisgender men and women are well established. No evidence exists regarding changes in myocardial mass or cardiac function parameters in transgender individuals undergoing gender-affirming hormone therapy (GAHT). Design, setting, participants, and main outcomes: A prospective study enrolling transgender individuals under GAHT (20 individuals assigned female at birth [AFAB] and 15 assigned male at birth [AMAB]) was conducted at the Medical University of Vienna from 2019 to 2022. A 3-Tesla electrocardiogram-gated magnetic resonance imaging measured myocardial mass, LVEF, and other cardiac function parameters before GAHT and at 6-month follow-up. Myocardial lipid content was quantified using magnetic resonance spectroscopy. Results: In AFAB, myocardial mass increased significantly after 6 months of GAHT from mean (±SD) 48 (±8) g/m ² at baseline to 54 (±7) g/m ² at follow-up (P = .011). Individuals assigned male at birth showed a nonsignificant decrease of 4 (±14) g/m ² in myocardial mass. In both groups, no significant changes were noted in LVEF, stroke volume, cardiac output, or peak filling rate. Neither testosterone (AFAB: r = −0.127, P = .679; AMAB: r = −0.127, P = .679) nor estradiol levels (AFAB: r = −0.154, P = .616; AMAB: r = −0.154, P = .616) nor body mass index was related to myocardial mass at follow-up. Brain natriuretic peptide levels in AFAB were significantly reduced at follow-up (from median [IQR] 41 [26-57] to 19 [12-34] pg/mL). Conclusions: Myocardial mass increased, while NT-proBNP levels decreased significantly in AFAB after 6 months of GAHT. However, no significant changes in cardiac function were noted in AMAB and AFAB.