CASR and autoimmune polyendocrine syndrome type 1: Familial hypoparathyroidism can occur as part of various genetic syndromes, such as autosomal dominant hypocalcemia (ADH), caused by activating mutations in the calcium-sensing receptor (CaSR), or as part of syndromic disorders like DiGeorge syndrome and autoimmune polyendocrine syndrome type 1 (APS-1).