The overall reason for altered osteocytic protein expression in CKD in general, and increased osteocytic FGF23 expression, in particular, remains unknown since these changes occur prior to the development of any detectable abnormalities in circulating mineral ion or hormone concentrations [21]; however, changes in osteocyte protein expression suggest that damage occurs to bone that is not detectable by traditional markers of mineral metabolism or by histomorphometry. This evidence concerns the gene FGF23 and chronic kidney disease.