BONE AND MINERAL METABOLISM IN AFRICAN-AMERICANS

Important differences exist in the metabolism of bone and mineral and the vitamin D endocrine system between whites and African Americans an d include rate of skeletal remodeling, bone mass, and vitamin D metabo lism. A higher bone mineral density (BMD) in African Americans is asso ciated with a diminished incidence of osteoporosis and fractures. Seru m 17 beta-estradiol and the rate of GH secretion are higher in black t han in white men, but there is no racial difference in women in this r egard. The mechanisms for reduced rate of skeletal remodeling and for greater BMD in blacks are not known, but diminished rate of skeletal r emodeling could be a contributing factor for greater bone mass. Reduct ion in serum 25-hydroxyvitamin D in blacks is attributed to increased skin pigment and to diminished dermal production of vitamin D-3 and co nsequent decreased hepatic synthesis of the metabolite. There is no ev idence that alteration of the vitamin D endocrine system contributes t o or is responsible for racial differences in skeletal remodeling and bone mass. Black infants, however, are at risk for developing vitamin D-deficient rickets, particularly when breast-fed. (C) 1997, Elsevier Science Inc.