Hypoparathyroidism Natural History Study

Inclusion Criteria: * An understanding, ability and willingness to fully comply with study procedures and restrictions. * Ability to voluntarily provide written, signed and dated informed consent as applicable to participate in the study. * Male or female ≥18 years of age with HPT. All HPT sub-types are eligible, including surgical (HPT-S) and nonsurgical (HPT-NS) HPT: autoimmune, genetic (including but not limited to: DiGeorge syndrome, autoimmune polyendocrine syndrome type 1, hypoparathyroidism sensorineural deafness and renal disease syndrome, Kearns-Sayre syndrome, mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes \[MELAS\] syndrome, mitochondrial trifunctional protein \[MTP\] deficiency syndrome, Kenny-Caffey syndrome, Sanjad-Sakati syndrome, autosomal dominant hypocalcemia), infiltrative (granulomatous), mineral deposition (copper, iron), metastatic, radiation and idiopathic HPT. * Diagnosis of HPT established based on historic hypocalcemia in the setting of inappropriately low serum PTH levels on two occasions. * All treatment regimens are permitted, including but not limited to conventional management with calcium (e.g. calcium citrate, calcium carbonate, etc), active vitamin D (calcitriol, alfacalcidol), parent vitamin D, magnesium, phosphate binders and thiazides. Use of PTH-like drugs are permitted. Exclusion Criteria: * Functional HPT * Transient HPT * Pseudohypoparathyroidism * Pregnancy