PTH and hypoparathyroidism: Isolated autoimmune hypoparathyroidism has also been described in adult patients who develop circulating antibodies targeted against the extracellular domain of the calcium-sensing receptor (CaSR).(93) These antibodies activate the receptor and thereby inhibit PTH secretion.(94–96) Patients with noncytotoxic anti-CaSR antibodies may recover from hypoparathyroidism over time as antibody titers decrease.