FGF23 and chronic kidney disease: Interestingly, in subjects with normal renal function, the rise of plasma PTH has been shown to precede the increase of plasma fibroblast-growth factor 23 (FGF23), an independent marker of poor renal and CV outcomes and mortality in CKD, whereas, in the course of CKD, whether PTH or FGF23 rises earlier depends on the status of vitamin D [31].