FGF23 and chronic kidney disease: Regarding the Vitamin D-FGF-23 axis, the HOST study (randomized and double blind on 1099 patients with CKD G4-G5) showed that plasmatic values of 25(OH)D were correlated with those of 1.25(OH)2D (r = 0.43) and iPTH (r = 0.25) and as after a 2.9-year follow-up patients who were in lowest tertile of 1.25(OH)2D values had an increased risk of death (HR, 1.33; 95% CI, 1.01–1.74) and initiation of chronic dialysis (HR, 1.78; 95% CI, 1.40–2.26) [34].