HYPERPARATHYROIDISM

abnormal increase in the secretion of parathyroid hormone by one or more parathyroid glands (see parathyroid gland). The oversecretion is usually caused by a tumour or enlargement of parathyroid tissue and results in elevated blood and urine calcium, elevated urine phosphorus, and low-to-normal blood phosphorus. The excess calcium is withdrawn from the bones, resulting in bone softening (osteomalacia) and an increased susceptibility to fracture. Other effects are kidney stones and decreased nervous and muscular excitability. Treatment is usually surgical removal of the tumour or excess parathyroid tissue, which may cause a transitory hypoparathyroidism (q.v.).