Vitamin D Metabolism and Its Role in Temporomandibular Joint Osteoarthritis and Autoimmune Thyroid Diseases.

The aim of this review was to present the metabolism of vitamin D, as well as to discuss the role of vitamin D in bone metabolism, temporomandibular joint osteoarthritis (TMJ OA), and autoimmune thyroid diseases (AITD) on the basis of the literature. Vitamin D plays a significant role in human health, as it affects the calcium-phosphate balance and regulates the bone metabolism. Calcitriol impresses the pleiotropic effect on human biology and metabolism. Its modulative function upon the immune system is based on the reduction of Th1 cell activity and increased immunotolerance. Vitamin D deficiency may lead to an imbalance in the relationship between Th1/Th17 and Th2, Th17/Th reg, and is considered by some authors as one of the possible backgrounds of autoimmune thyroid diseases (AITD), e.g., Hashimoto's thyroiditis or Graves' disease. Moreover, vitamin D, through its direct and indirect influence on bones and joints, may also play an important role in the development and progression of degenerative joint diseases, including temporomandibular joint osteoarthritis. Further randomized, double blind studies are needed to unequivocally confirm the relationship between vitamin D and abovementioned diseases and to answer the question concerning whether vitamin D supplementation may be used in the prevention and/or treatment of either AITD or OA diseases.