Cloning of the CaR was immediately followed by the association of human genetic diseases with inactivating or activating CaR mutations: familial hypocalciuric hypercalcemia (FHH) and neonatal severe hyperparathyroidism (NSHPT) are caused by CaR-inactivating mutations, whereas autosomal dominant hypoparathyroidism is secondary to CaR-activating mutations [1]. The gene discussed is CASR; the disease is neonatal severe primary hyperparathyroidism.