Résumé
Vitamin D is the precursor of 1, 25-dihydroxyvitamin D, which is considered as the critical hormone involved in the regulation of calcium and phosphate homeostasis and bone metabolism. Adequate vitamin D status is very important in the maintenance of bone health. However, recent controlled vitamin D intervention studies showed controversial results. One of the important reasons for this is the difference in the baseline of vitamin D status among studies. The vitamin D status in the Chinese population is much lower as compared to that in Western countries. Postmenopausal women and elderly with vitamin D deficiency should take appropriate vitamin D supplementation in order to achieve serum 25-hydroxyvitamin D levels greater than 20 ng/ml or even 30 ng/ml. However, it may be difficult to bring more benefits from excessive supplementation in order to maintain bone health.
Résumé
Vitamin D participates in a variety of biological processes. 1,25-dihydroxyvitamin D [1,25-(OH)2D]is the active form of vitamin D. Besides its classical role in bone and calcium homeostasis, 1,25-(OH)2D has many non-classical functions such as regulating proliferation and differentiation of cells in various tissues, including tumor cells as well. However, the role of 1,25-(OH)2D in thyroid cancer is not clear yet. There are three integral components of the vitamin D pathway in thyroid cells. These components are the vitamin D receptor, 1α-hydroxylase (CYP27B1), and 24-hydroxylase (CYP24A1). Differences in the expression levels of these components in normal thyroid tissue and thyroid cancer tissue may offer clues and lay the foundation for study of the inhibitory function in the pathogenesis of thyroid cancer.This review focuses on the insights gained in the elucidation of the role of 1,25-(OH)2D pathway in thyroid cancer, one of the most common endocrine malignancies.