Vitamin D and the thyroid

Vitamin D deficiency has been implicated in the pathogenesis of several disease processes ranging from autoimmune disease to malignancy. Knowledge in the area of vitamin D deficiency has grown exponentially over recent years, and relationships between vitamin D and many disease conditions, including benign and malignant thyroid disease, have been discovered. Thyroid tissue expresses vitamin D receptors and in vitro studies have shown that 1,25(OH)2D (calcitriol) decreases proliferation and increases markers of differentiation in thyroid cancer cells. Vitamin D deficiency has also been found to have direct effects on thyroid function, playing a role in autoimmune hypo-and hyperthyroidism. This chapter will review the role of vitamin D in the thyroid by specifically looking at the function of vitamin D at the cellular level and its effects in both benign and malignant thyroid disease.