Endocrine Abstracts

Fibroblast Growth Factor 23 (FGF23) is a hormone synthesized by bone osteocytes that controls serum phosphate concentrations by increasing renal phosphate excretion and decreasing renal production of 1,25-dihydroxyvitamin D3. Although this role has been known for several decades, the mechanisms that determine the regulation of FGF23 synthesis and secretion in response to variations in serum phosphate concentration are still poorly understood. In this talk, I will present data implicating PiT1/PiT2 transceptors expressed in bone in this sensing role and thus influencing the kidney (bone to kidney), and I will also present recent data illustrating the role of the kidney, a target of FGF23, in the endocrine regulation it exerts on bone to control FGF23 secretion (kidney to bone). Knowledge of these reciprocal regulatory loops will provide a better understanding of disorders of FGF23 homeostasis, which are often associated with significant morbidity and mortality.