Gender-affirming hormone therapy modifies body composition and lean muscle mass in transgender persons. A recent analysis published in CJASN examined the effects of masculinizing and feminizing gender-affirming hormone therapy on markers of kidney function.
For the analysis, a team led by David Collister, MD, PhD (University of Alberta) searched the medical literature and identified 26 relevant studies. At 12 months after initiating gender-affirming hormone therapy, blood levels of creatinine (a marker of kidney function) increased by 0.15mg/dL in transgender men and decreased by -0.05mg/dL in transgender women. (An increase in creatinine may indicate possible kidney dysfunction or simply reflect a change in underlying lean muscle mass.) No study reported the impact of gender-affirming hormone therapy on other markers or measures of kidney function (e.g. albumin or protein in the urine, cystatin C, directly measured kidney function), indicating the need for additional research.

"It is important to understand how gender-affirming hormone therapy impacts kidney physiology and how it changes values of common laboratory tests so that patients are properly assessed and not mislabeled with health or disease with regards to kidney function," said Dr. Collister.
An accompanying editorial notes that the analysis raises several important questions that should be the focus of subsequent investigations, most notably the mechanism through which gender-affirming hormone therapy is associated with changes in creatinine and whether it independently affects kidney function.
Additional study authors include Emily Krupka, BSc, Sarah Curtis,Thomas Ferguson, MSc, Reid Whitlock, MSc, Adam C. Millar MD, MScCH, Marshall Dahl, MD, Raymond Fung, MD, Sofia B. Ahmed, MD, MSc, Navdeep Tangri, MD, PhD, and Michael Walsh, MD, PhD.
Reference:
"The Effect of Gender-Affirming Hormone Therapy on Measures of Kidney Function: A Systematic Review and Meta-Analysis," Emily Krupka, BSc, Sarah Curtis,Thomas Ferguson, MSc, Reid Whitlock, MSc, Adam C. Millar MD, MScCH, Marshall Dahl, MD, Raymond Fung, MD, Sofia B. Ahmed, MD, MSc, Navdeep Tangri, MD, PhD, and Michael Walsh, MD, PhD, doi: 10.2215/CJN.01890222.