Vitamin D deficiency is related to thyroid antibodies in autoimmune thyroiditis

Introduction: It has been known that vitamin D has some immunomodulatory effects and in autoimmune thyroid diseases, vitamin D deficiency was more prevalent. In this study, our aim was to investigate the relationship between thyroid autoantibodies and vitamin D. Material and methods: Group 1 and 2 consisted of 254 and 27 newly diagnosed Hashimoto's thyroiditis (HT) and Graves' disease (GD) cases, respectively; age-matched 124 healthy subjects were enrolled as controls (group 3). All subjects (n = 405) were evaluated for 25OHD and thyroid autoantibody [anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-tg)] levels. Results: Group 2 and group 1 patients had lower 25OHD levels than group 3 subjects 14.9 +/- 8.6 ng/ml, 19.4 +/- 10.1 ng/ml and 22.5 +/- 15.4 ng/ml, respectively (p < 0.001). Serum 25OHD levels inversely correlated with anti-tg (r = -0.136, p = 0.025), anti-TPO (r = -0.176, p = 0.003) and parathormone (PTH) (r = -0.240, p < 0.001). Group 2 patients had higher anti-tg and anti-TPO levels than group 1 and 3 (p < 0.001). Conclusions: In this study, we found that patients with autoimmune thyroid disease (AITD) present with lower vitamin D levels and GD patients have higher prevalence. Since we found an inverse correlation between vitamin D levels and thyroid antibody levels, we may suggest that vitamin D deficiency is one of the potential factors in pathogenesis of autoimmune thyroid disorders.