Compared to CKD patients who received a kidney transplant, dialysis patients have higher serum FGF23 levels and develop cardiac fibrosis, but cardiac FGFR4 expression levels do not correlate with fibrosis (188), further supporting the notion that cardiac FGF23/FGFR4 signaling might not directly contribute to fibrosis. Here, FGF23 is linked to chronic kidney disease.