Background: Sex hormones are believed to play an important role in the development and progression of cardiovascular disease. However, the gender gap in onset and mortality is not yet completely understood. Transsexuals undergoing hormone therapy are a promising collective for analyzing the effects of sex hormones on atherosclerosis and other cardiovascular disease. Objectives of the study: To identify gender-specific cardiovascular changes attributed to high-dose hormone therapy in male-to-female (MtF) and female-to-male(FtM) transgender using sonography and magnet resonance spectroscopy. Study design: Longitudinal cohort study. Transsexuals will undergo two 3 Tesla MRI scan sessions: 1. baseline (before hormone treatment) and 2. after 6 months of treatment. An oral glucose tolerance test (OGTT) will be performed at baseline and 6 months after treatment onset. An overall study duration of 12 months is proposed. Materials and

Methods: MRI measurements will be performed on a 3 Tesla scanner. Study population: 10 FtM, 10 male-to-female MtF transsexuals (aged 18-50), free of hormone-medication at baseline. Relevance and implications of the study: Changes in atherosclerotic risk due to hormone therapy have been studied to no definite results and so far, little is known about the effects of hormone therapy on hepatic and myocardial fatty tissue. Hence this study will provide important new data on the broad clinical aspects of sex hormones as hormone replacement therapy in particularly opposite-sex hormone therapy.