Background: Parathyroid disorders are very common in the general population and include disorders of parathyroid excess, deficiency, or defects in parathyroid hormone (PTH) signaling. PTH, the main secretory product of parathyroid glands is responsible for regulation of calcium-phosphate homeostasis.

Objective: i) To investigate the cause of parathyroid disorders ii) To describe evolution, natural history, and longitudinal trends of parathyroid and related disorders seen in syndromic presentations like multiple endocrine neoplasia, hyperparathyroidism-jaw tumor syndrome

Eligibility: People ages 6 months older who have, are at risk of having, or are related to a person with a parathyroid or related disorder.

Design: Participants will be screened with a review of their medical records. Participants will be seen, tested, and treated by doctors based on their condition. Their visits may be in person or via telehealth. Participants will complete questionnaires. They will answer questions about their physical, mental, and social health. Participants may give samples such as saliva, blood, urine, or stool. Participants may give cheek cell samples. They will do this using a cheek swab or by spitting into a cup. Adult participants may give a skin biopsy. For this, a small bit of skin is removed with a punch tool. Participants may have medical photos taken. If participants have surgery during the course of their regular care either at the NIH or at a different hospital or doctor s office, researchers will ask for some of the leftover tissue. Participants will be in the study as long as they are being seen by their doctor.