The Ca-sensing receptor (CaSR), first identified and cloned in 1994,13 is thought to be the prime regulator of iPTHsecretion14–15 and as such has become the target for newer therapies in the treatment of both primary and secondary hyperparathyroidism.16,17 Cinacalcet is a type II calcimimetic that acts as an allosteric modulator of the CaSR on the parathyroid cells to increase its sensitivity to extracellular Ca ions and diminish iPTH secretion in response.18 Cinacalcet shifts the set point for Ca-regulated iPTH secretion to the left leading to a reduction in iPTH secretion.7 Here, CASR is linked to secondary hyperparathyroidism.