FGF23 and Hypocalcemia: Hypophosphatemia (1.7 mg/dL) and an abnormally low level of 1,25(OH)2 vitamin D (15 pg/mL), hypophosphatemia (1.7 mg/dL), hypocalcemia (8.3 mg/dL), high serum ALP (1639 UI/L), high intact PTH (103.3 pg/mL), and low tubular resorption of phosphorus clearance (%TRP) (67.7%). The 1,25(OH)2 vitamin D3 level was 96.3 pg/mL. Importantly, the serum FGF‐23 level was elevated to 1500 pg/dL.