Vitamin D deficiency is associated with thyroid autoimmunity: results from an epidemiological survey in Tianjin,...

The pathogenesis of Hashimoto's thyroiditis (HT) is unclear, although some studies have identified an association between vitamin D deficiency and thyroid autoantibody positivity. This study aimed to investigate vitamin D status, and its relationships with thyroid autoantibody positivity and HT, via a large epidemiological survey.

The epidemiological survey was conducted in Tianjin, China. All participants underwent testing for serum 25-hydroxyvitamin D (25OHD), thyroid function, and thyroid autoantibodies, and some participants underwent testing to evaluate CD4⁺ T-cell differentiation and concentrations of related cytokines.

The study included 1812 participants and revealed prevalences of 13.1% for thyroid peroxidase antibodies (i-TPOAb) and 14.0% for thyroglobulin antibodies (i-TgAb). Logistic regression analysis revealed that thyroid autoantibody positivity was associated with sex, age, and 25OHD classification. An increased likelihood of i-TPOAb positivity was associated with 25OHD deficiency (odds ratio [OR]: 2.428, 95% confidence interval [CI]: 1.383-4.261) and 25OHD inadequacy (OR: 1.198, 95% CO: 0.828-1.733; p = 0.008). An increased likelihood of i-TgAb positivity was associated with 25OHD deficiency (OR: 2.366, 95% CI: 1.366-4.099) and 25OHD inadequacy (OR: 1.263, 95% CI: 0.883-1.807; p = 0.009). Relative to healthy subjects, patients with HT had significantly higher proportions of Th1 and Th17 cells, as well as higher concentrations of related cytokines.

This study revealed that vitamin D deficiency was associated with thyroid autoantibody positivity, and that vitamin D deficiency seems to be involved in the pathological mechanism underlying HT. Large randomized controlled trials are needed to investigate the effects of vitamin D supplementation on HT.