The most important ones are those that cause familial hypocalciuric hypercalcemia (FHH), neonatal severe hyperparathyroidism, or autosomal dominant hypocalcemia (ADH), in which loss-of-function mutations in CaSR (for instance, CaSR-R392X) promote disruption of the downregulation mechanisms of PTH secretion [18]. This evidence concerns the gene CASR and familial hypocalciuric hypercalcemia.