**5. Conclusions**

Loss of kidney function is accompanied by an accumulation of renalase in blood serum.


**Author Contributions:** Conceptualization, W.K.; methodology, W.K. and N.M.S.; statistical analysis, B.G.; investigation, E.C.-H.; resources, A.G.; writing—original draft preparation, W.K.; writing review and editing, B.D. and K.C.; supervision, M.W.; funding acquisition, K.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee of Pomeranian Medical University in Szczecin (No. KB-0012/07/17 from 16 January 2017).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript or in the decision to publish the results.
