THE VITAMIN-D-RECEPTOR GENE AND CALCIUM-METABOLISM

Dietary Ca2+ is essential for the development and maintenance of bone mineral mass. The vitamin D endocrine system plays a fundamental role in the regulation of Ca2+ homeostasis, and mutations affecting genes i mplicated in vitamin D metabolism or vitamin D receptor (VDR) function s ave responsible for severe alterations in skeletal growth. In additi on, vitamin D is also implicated in the pathophysiology and treatment of adult bone disorders associated with impaired mineralization of bon e matrix. Very recently, common polymorphisms in the 3'- and 5'-end re gion oft he VDR gene have been suggested as possible determinants of b one mineral mass and, hence of the risk of osteoporosis. None of these polymorphisms appear to be associated unequivocally with bone mineral mass or biochemical variables of Ca2+ and phosphate metabolism, excep t perhaps VDR 3'-end polymorphisms before puberty. As these associatio ns ave so inconsistent, interactions with environmental factors, parti cularly dietary intake, and with other polymorphisms have to be consid ered.