Dietary Phosphorus Regulates Serum Fibroblast Growth Factor-23 Concentrations in Healthy Men

Context: Fibroblast growth factor 23 (FGF-23) is important in the regulation of phosphorus and vitamin D metabolism. States of excess circulating FGF-23 are associated with renal phosphate wasting and inappropriately low serum 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations. Conversely, states of absent or biologically inactive circulating FGF-23 are associated with increased serum phosphorus and 1,25(OH)2D concentrations. Restriction of the dietary intake of phosphorus increases renal phosphate reabsorption and 1,25(OH)2D production, whereas the opposite occurs when dietary phosphorus is supplemented. Objective: We sought to determine whether serum FGF-23 concentration is regulated by dietary phosphorus and thereby mediates the physiological response of serum 1,25(OH)2D to changes in dietary phosphorus. Design, Setting, and Participants: We studied 13 healthy men as inpatients during a 4-wk dietary phosphorus intervention study. Intervention: Subjects consumed a constant diet that provided 500 mg of ...