Patients whose parathyroid activity is elevated above normal are referred to as having hyperparathyroidism. This study will help researchers better understand the causes of hyperthyroidism and to evaluate and improve methods for diagnosis and treatment.

In this study, patients diagnosed with or suspected of having hyperparathyroidism will be selected to participate. In addition, patients with related conditions such as parathyroid tumors, will also be selected.

Subjects will be asked to provide blood and urine for testing to confirm their condition. They will then be surgically treated by removal of the parathyroid gland(s) (parathyroidectomy).

Subjects with parathyroid tumors will undergo several diagnostic tests to determine the exact location of the tumor as well as the tumor's activity. The tests may include; ultrasounds, nuclear scanning, CT scans, MRI, and specialized blood testing.

Sometimes parathyroidectomy leads to hypoparathyroidism. Options for treating the patients after the surgical procedure will also be addressed. Calcium and Vitamin D supplements are typically the mainstay of post parathyroidectomy therapy. Other potential treatments include transplanting the parathyroid gland(s) to other areas of the body.