Fibroblast growth factor 23 (FGF 23) and phosphocalcic metabolism in chronic kidney disease

The ample information available in relation to FGF 23, calcium, phosphorus, PTH, and 25/1,25 vitamin D has allowed us to define consistent values for each variable in each stage of chronic kidney disease (CKD). These values can define early stages, prognostic issues, and new treatment targets. We describe a cross-sectional study of these parameters in patients with different stages of CKD. We measured FGF 23 by ELISA (intact molecule, Kainos Laboratory, Japan), calcium, phosphorus, PTH and vit D by standard methods. We examined 251 patients, 146 of which were men, with a mean age of 62.5 (11.5) years and 43% prevalence of type II DM. Levels of FGF 23 rose progressively, in a very significant manner, in correlation with the evolution of CKD, especially in stage 4 as compared to stage 1 (110.61 ng/L vs 31.32 ng/L). The same happened with iPTH values. Additionally, levels of 1,25 vitamin D decreased in a similar manner. Calcium values did not change. 25 vit D3 levels were low at all times and showed no tendency for a steady decline. Phosphorus rose in stage 4 CKD. Levels of FGF 23 were negatively correlated with renal function indicators and positively correlated with PTH and P. During the evolution of CKD, changes of FGF 23 and PTH would be the earliest markers. Calcium and 25 vit D3 do not vary with changes in the progression of CKD. Values of FGF 23 show an important correlation with PTH, 1,25 vit D3, P and estimated glomerular filtration rate.