NCI: Hyperfunction of the parathyroid glands resulting in the overproduction of parathyroid hormone. It is caused by parathyroid adenoma, parathyroid hyperplasia, parathyroid carcinoma, and multiple endocrine neoplasia. It is associated with hypercalcemia and hypophosphatemia. Signs and symptoms include weakness, fatigue, nausea, vomiting, constipation, depression, bone pain, osteoporosis, cystic bone lesions, and kidney stones.,MSH: A condition of abnormally elevated output of PARATHYROID HORMONE due to parathyroid HYPERPLASIA or PARATHYROID NEOPLASMS. It is characterized by the combination of HYPERCALCEMIA, phosphaturia, elevated renal 1,25-DIHYDROXYVITAMIN D3 synthesis, and increased BONE RESORPTION.