In our study, irisin levels before transplantation were low in patients with BMI above and below 30; only after the kidney transplantation procedure and the introduction of diabetogenic immunosuppressive drugs did a large difference in irisin levels appear, levels significantly higher in obese patients, which seems to be consistent with the theory of an adaptive increase in irisin levels in patients with metabolic abnormalities associated with obesity [10]. Here, FNDC5 is linked to obesity due to melanocortin 4 receptor deficiency.