FGF23 and chronic kidney disease: Compared to controls, median levels of sclerostin and intact PTH became elevated in CKD 3 (p = 0.018 and 0.022, respectively) (Figure 3), while median levels of 1,25D fell and FGF23 levels increased in CKD 4/5 (p = 0.008 and p < 0.001, respectively) (Figure 3).