Activating mutations of the CaSR result in hereditary hypoparathyroidism, which is characterized by marked hypercalciuria [21]. Many patients with advanced CKD have secondary hyperparathyroidism (high PTH) and unlike primary hyperparathyroidism; they have low or low normal Ca+2 due to calcitriol deficiency. This evidence concerns the gene CASR and primary hyperparathyroidism.