Association Between Chronic Kidney Disease Stage and Circulating FGF23 Cleavage Intensity in Patients With Chronic Kidney Disease

This cross-sectional proof-of-concept study aims to investigate the relationship between chronic kidney disease (CKD) severity and circulating FGF23 (fibroblast growth factor 23) cleavage intensity estimated by the iFGF23/cFGF23 ratio. Eighty male patients aged 55-75 years with CKD stages 3a to 5 will be included (20 per stage). Blood samples obtained during routine nephrology care will be supplemented by two additional tubes to measure iFGF23, cFGF23, hepcidin, erythropoietin, 1,25-vitamin D and TRAP5b. The primary endpoint is the iFGF23/cFGF23 ratio. Secondary analyses will evaluate the associations between FGF23 forms and renal, hematological, iron metabolism and mineral bone parameters. This study will provide the first human data on FGF23 cleavage alterations across CKD stages and may identify novel biomarkers for anemia and cardiovascular complications.