FGF23 and hypophosphatemia: Biochemical evaluation at admission showed hypophosphatemia due to low renal tubular reabsorption of phosphate (TmP/GFR: 1.70 mg/dL) and increased serum intact FGF23 value (iFGF23) (190 pg/mL, n.v.: < 95 pg/mL, DiaSorin kit, Stillwater, MN, USA) suggestive of TIO.