FGF23 and hyperparathyroidism: After renal transplantation, FGF23‐mediated hypophosphatemia and hyperparathyroidism may be coincident.(5) After intravenous iron infusion, hypophosphatemia caused by FGF23‐mediated phosphaturia is commonly observed.(39, 40, 47) This lowering of TmP/GFR after iron infusion is likely to be augmented if patients have secondary hyperparathyroidism.