[Fibroblast Growth Factor 23-Klotho: a new axis of phosphate balance control]

The kidney is a key player of phosphate balance, it determines serum phosphate levels by coupling phosphate reabsorption in the renal proximal tubule, calcitriol synthesis and consequently intestinal -phosphate absorption. The identification of fibroblast growth factor 23 (FGF23) as a hormone regulating phosphate and calcitriol metabolism has unveiled the mechanisms that coordinate these renal proximal tubule functions. A bone-kidney axis has emerged that controls bone mineralization. Animal model studies have improved our understanding of phosphate homeostasis and revealed the role of the Klotho protein, which is mandatory to FGF23 action. In this review, we detail FGF23 and Klotho implication in physiology and in genetic or acquired disorders. Phosphate ion is involved in vascular and soft tissue calcification and is important for cell proliferation. Disorders of FGF23-klotho axis alter life span and are involved in senescence.