Calcium regulation.

Normal calcium regulation depends on the complex interactions of several systems. The specific calcium regulating hormones, parathyroid hormone, calcitriol and calcitonin, affect calcium and phosphorus concentration and supply by acting on bone, kidney and intestine. The changing concentration and supply of ions not only regulate these hormones, but may also influence the function of the target organs, particularly bone, directly. Systemic hormones such as growth hormone and somatomedins, glucocorticoids, sex hormones and thyroid hormone are essential for skeletal growth and development and interact with calcium regulators. Prostaglandins and osteoclast activating factor may be important in local regulation of bone. Disorders of calcium regulation are common, particularly hypercalcemia; however, measurements of parathyroid hormone are not yet ideal and the factors which produce hypercalcemia in malignancy have not been identified. The role of calcium regulating hormones in the pathogenesis and treatment of osteoporosis is controversial. Solution to these problems may be dependent on the identification of additional factors which influence mineral metabolism.