Recent advances in the understanding of the metabolism and functions of vitamin D.

Many advances have been made in the past several years in our understanding of the metabolism and mechanism of action of vitamin D. Recognition of the clinical implications of this knowledge continues to grow. Despite these gains, however, many questions remain unanswered. These include the role of 24,25(OH)2D3 in physiologic processes, the nature of the contribution of vitamin D metabolism to bone growth and development, the responses of other possible target tissues such as the pancreas and parathyroid gland, and the further elucidation of interactions between vitamin D metabolites and parathyroid hormone in the maintenance of calcium and phosphorus homeostasis. The next decade of research is bound to bring insight into these and other questions.