ADH1 and ADH2 Disease Monitoring Study (DMS)

Key Inclusion Criteria: * Have a documented activating variant or variant of uncertain significance of the CASR gene causative of ADH1 or documented activating variant or variant of uncertain significance of the GNA11 gene causative of ADH2 associated with a clinical syndrome of hypoparathyroidism prior to enrollment Note: Acceptable documentation includes CASR or GNA11 genetic analysis report. If no prior documented CASR or GNA11 gene variant or variant of uncertain significance, potential participants can undergo CASR and GNA11 gene variant analysis at Screening. * Be willing and able to provide informed consent or assent after the nature of the study and its details have been explained, and prior to any research-related procedures * Be willing and able to provide access to prior medical records including imaging, biochemical, and diagnostic and medical history data, if available * Be willing and able to comply with the study visit schedule and study procedures Key Exclusion Criteria: * Have serious medical or psychiatric comorbidity that, in the opinion of the Investigator, would present a concern for participant safety or compromise the ability to provide consent or assent, or comply with the study visit schedule and study procedures * Enrollment in an interventional clinical study at the time of DMS Screening visit Note: Other protocol defined Inclusion/Exclusion criteria may apply.