Fibroblast growth factor: will this hormone be the hemoglobin A1c for managing phosphorus balance in chronic kidney disease?

Fibroblast growth factor 23 (FGF23) is a bone-derived hormone that regulates phosphorus and vitamin D metabolism by increasing the rate of urinary excretion of phosphate and by inhibiting the renal production of 1,25-dihydroxyvitamin D.1 In patients with chronic kidney disease (CKD), circulating FGF23 levels rise progressively as a physiological adaption to compensate for persistent phosphate retention and increased total body phosphorus.2,3 Elevated phosphate levels and depressed 1,25-dihydroxyvitamin D levels are associated with increased mortality among patients with CKD. Recently, increased FGF23 levels have been associated with mortality, left ventricular hypertrophy, endothelial dysfunction, and progression of CKD independent of serum phosphate levels.4 Fibroblast growth factor 23 is emerging as an attractive biomarker for identifying which patients with CKD might benefit most from aggressive management of their hyperphosphatemia.5 It is currently not known whether FGF23 exerts direct end organ toxicity, such as in the heart, vessels, and kidneys, or whether it is a marker for damage.6