Factors Affecting Calcium Metabolism in （钙代谢影响因素）.pdf

ANNALS OF CLINICAL AND LABORATORY SCIENCE, Vol. 11, No. 4 Copyright © 1981, Institute for Clinical Science, Inc. Factors Affecting Calcium Metabolism in Disorders of the Kidney* MURRAY J. FAVUS, M.D. Departm ent of Medicine, Michael Reese Hospital and Medical Center, and the University o f Chicago Pritzker School o f Medicine, Chicago, IL 60616 ABSTRACT The ionized calcium concentration in blood is maintained within narrow limits by a complex hormonal system that includes parathyroid hormone (PTH) and vitamin D. The kidney plays a pivotal role in the physiologic action of PTH, as this peptide hormone increases tubular calcium reabsorp­ tion, decreases tubular phosphate reabsorption, and stimulates the renal 25-hydroxy-1-hydroxylase to convert 25-hydroxyvitamin D to 1,25-dihy- droxyvitamin D, the hormonal form of the vitamin that stimulates intestinal calcium absorption. Inherited and acquired disorders of tubular function and acute and chronic renal failure may disturb normal renal handling of calcium and phosphorus and the hydroxylation of 25-hydroxyvitamin D. As a result, decreased intestinal calcium absorption and hypocalcemia cause parathyroid hyperplasia and metabolic bone disease. Introduction of absorbed dietary calcium could cause fluctuations in blood calcium concentra­ A complex hormonal system regulates tion. As such perturbations would disturb the distribution and concentration of cal­