Comparison of renal function estimation in transgender adults

Purpose: Renal function assessment typically relies on equations such as Cockcroft-Gault (CG) or Modification of Diet in Renal Disease (MDRD) which consider age, weight, sex, and serum creatinine (SCr). In transgender patients, sex assigned at birth and hormone therapy (HT) may influence renal function estimation. The purpose of this study is to compare renal function estimation among transgender patients with or without HT to identify the most accurate equation. Methods: In this retrospective, matched, case-control study, patients >18 years from a transgender clinic with at least one SCr measurement were included as cases. Cases were matched to a sex assigned at birth and a transition gender control based on age and weight. Comparisons of SCr and CrCl as calculated using CG and MDRD between cases and controls, sex, and HT were completed. Results: 248 matches were included in the initial analysis. Of transgender cases, 148 (60%) were transgender women. Between matched pairs, there was no significant difference in SCr or CrCl estimation using CG or MDRD, regardless of sex assigned at birth. Transgender women taking HT significantly affected SCr (p< .01) and CrCl estimation using MDRD (p< .01), but not CG (p=.21). Transgender men taking HT had significant differences in SCr and CrCl estimation based on CG and MDRD calculations (p< .01). Conclusion: Among transgender patients receiving HT, discrepancies in renal function estimates may occur based on equation type and HT use. Clinicians should exercise prudence utilizing renal function estimates to adjust renally-excreted medications in this population.