Serum levels of intact PTH (normal, <60 pg/mL), calcium (normal, 2.33 to 2.74 mmol/L), and phosphorus (normal, 1.55 to 2.65 mmol/L) during the initiation of cinacalcet. Cinacalcet was initiated on day zero and, because of the robust response, it was briefly held on day 4 and restarted on day 5.