PMC4324571_01
Overview of FGF23 physiology. (+) corresponding to a positive effect. (-) corresponding to an inhibitory effect DMP1: dental matrix protein 1. FGF23: fibroblast growth factor 23. FGFR1: fibroblast growth factor receptor type 1. PHEX: phosphate-regulating gene with homologies to endopeptidases on X chromosome. PTH: parathyroid hormone. Npt 2: type II sodium-phosphate cotransporters (type a and c)
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F2
Since FGF23 has been recently shown to be a cornerstone of phosphate/calcium/vitamin D metabolism, an overview of its physiology is shown in Figure 2.
Evaluation of an adult patient with hypophosphatemia. TmP/GFR: tubular maximal reabsorption of phosphorus / glomerular filtration rate FE phosphorus: fractional excretion of phosphorus. PTH: parathyroid hormone
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F3
When evaluating a patient with hypophosphatemia (Figure 3), serum phosphorus levels should be interpreted with concomitant evaluations of serum total and ionized calcium, PTH and 25-OH vitamin D, as well as urine phosphate and calcium excretion since isolated serum phosphate levels are not reliable indicators of total body phosphate content.