Kidney clearance of fibroblast growth factor-23 in humans.

PURPOSE OF REVIEW: Recent studies have shed light on factors influencing FGF23 regulation in terms of its production and cleavage. However, less is known about FGF23 elimination from circulation. The kidney's role in FGF23 elimination will be the focus of this review.

RECENT FINDINGS: Marked abnormalities in FGF23 physiology have been observed in persons with reduced kidney function compared with healthy persons and raise the question of whether the kidney may be directly regulating FGF23 concentrations. FGF23 concentrations rise dramatically after onset of acute kidney injury and early chronic kidney disease and are associated with poor clinical outcomes. New studies leveraging measurements of FGF23 in the aorta and renal veins concurrently demonstrate that the human kidney efficiently extracts both intact and C-terminal FGF23 from the circulation independent of kidney function and catabolize the hormone. Additionally, the kidney's reduction of PTH predicts the amount it will reduce both C-terminal and intact FGF23.

SUMMARY: The human kidney removes both intact FGF23 and its C-terminal fragments. FGF23 catabolism within the kidney may be influenced by PTH concentrations, and other factors. Future studies to understand regulation of these hormones and the kidney's role in this interplay are timely.