Abstract
There are known sex (i.e., biological) and gender (i.e., social) differences in the epidemiology and outcomes of chronic kidney disease. In this issue of the JCI, van Eeghen et al. provide a prospective multicenter observational study of transgender individuals initiating masculinizing and feminizing hormone therapy. Testosterone and estrogen with testosterone blockade had differential effects on kidney physiology including renal plasma blood flow, measured glomerular filtration rate, tubular biomarkers, and various proteins involved in inflammatory and repair pathways. The findings suggest that estrogen is renoprotective and that testosterone may be harmful to kidney function, but requires validation in larger, more diverse cohorts. The insights gained also need to be examined in the context of both endogenous and exogenous sex hormones in individuals over the life cycle.