Abstract
This chapter talks about vitamin D production, metabolism, mechanism of action, and clinical requirements. It discusses transport of vitamin D in the blood. The chapter focuses on internalization of vitamin D metabolites. It describes the regulation of calcium and phosphate metabolism. The chapter discusses classical target tissues of bone, intestine and kidney, and nonclassical target tissues of parathyroid glands and pancreas. It explains the immunobiology of vitamin D, and keratinocyte function in epidermis and hair follicles. Finally, the chapter deals with nutritional considerations and vitamin D treatment strategies.