Leipzig Team Prepares 2027 Cohort to Track Metabolic and Vascular Shifts From Gender-Affirming Hormones

The planned extension builds on the first HHS cohort of roughly 40 individuals examined before and at three, six, 12 and 24 months after starting estrogen-plus-blocker or testosterone regimens. Indirect calorimetry already showed shifts in resting energy expenditure; the new metabolic chamber will add precision while carotid and brachial artery testing will quantify endothelial function and blood-flow changes. MRI collaboration with the Max Planck Institute targets sexually dimorphic brain regions.

Observational pre-post design controls for individual baseline differences better than cross-sectional comparisons, yet lacks randomization and will remain vulnerable to unmeasured lifestyle or adherence confounders. Absolute effect sizes from the 2026 Communications Medicine temperature-perception paper were modest and equivalent to the cisgender sex difference, indicating the magnitude of hormone-driven plasticity rather than clinical risk.

Results could inform dosing adjustments for transgender patients and refine models of estrogen-testosterone action on muscle-fat partitioning and vascular stiffness in the wider population. Next required step is an RCT or large registry linkage to link these physiological markers to hard outcomes such as cardiovascular events or fracture rates over five to ten years.