[Limitations in the Interpretation of Kidney Function Markers During Testosterone Replacement Therapy].

Changes in kidney function parameters in men receiving testosterone replacement therapy (TRT) may influence the clinical assessment of treatment safety. However, the physiological meaning of these changes remains uncertain. In most cases, kidney function during TRT is evaluated using surrogate laboratory markers rather than glomerular filtration rate (GFR) measured with exogenous filtration markers. This creates a risk of misinterpretation, as the observed changes may reflect not only true alterations in glomerular filtration, but also therapy-related effects and patient phenotype-related characteristics. Existing studies do not allow a reliable distinction to be made between true changes in filtration function, changes in the characteristics of the marker used, or a combination of both, since most of them rely on surrogate indicators without comparison with measured GFR. Therefore, the question of what changes in kidney function parameters during TRT actually mean, and how they should be interpreted, remains unresolved.