Also, patients with Familial hypocalciuric hypercalcemia (FHH), a rare inherited disease with mutation in CaSR, could also result in hypercalcemia because the inactive CaSR in the parathyroid gland will lead to a slight elevation of PTH, similar to the hyperparathyroidism discussed above (Carroll and Schade, 2003). Here, PTH is linked to familial hypocalciuric hypercalcemia.