Together with our finding of a tendency for a negative association of serum FGF23 with log[1,25(OH)2D/25(OH)D], these results indicate that FGF23 may augment the reduction of serum 1,25(OH)2D by inhibition of 1α(OH)ase and attenuate the reduction of serum 24,25(OH)2D by stimulation of 24(OH)ase in CKD patients, which is in good agreement with previous findings obtained in our study of non-CKD patients19. This evidence concerns the gene FGF23 and chronic kidney disease.