The pleiotropic actions of vitamin D

General knowledge of the role of vitamin D3 in human physiology has been shaped by its discovery as a preventive agent of nutritional rickets, a defect in bone development due to inadequate uptake of dietary calcium. Studies on the function of the biologically active vitamin D3, 1,25-dihydroxyvitamin D3, have been greatly accelerated by the molecular cloning and structural analysis of the vitamin D3 receptor, which is a ligand-activated regulator of gene transcription. Molecular genetic techniques including genomics have helped to reveal that 1,25-dihydroxyvitamin D3 can control more than calcium homeostasis. It has effects on cellular differentiation and proliferation, and can modulate immune responsiveness, and central nervous system function. Moreover, accumulating epidemiological and molecular evidence suggests that 1,25-dihydroxyvitamin D3 acts as a chemopreventive agent against several malignancies including cancers of breast, prostate and colon.