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Lower Serum 25-Hydroxyvitamin D Level is Associated With 3 Types of Autoimmune Thyroid Diseases.
Ma, Jie MD; Wu, Di MBBS; Li, Chenyang MD; Fan, Chenling MBBS; Chao, Nannan MBBS; Liu, Jing MBBS; Li, Yushu MD, PhD; Wang, Renee MBBS; Miao, Wei MBBS; Guan, Haixia MD, PhD; Shan, Zhongyan MD, PhD; Teng, Weiping MD
[Article] Medicine. 94(39):e1639, September 2015.

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Autoimmune thyroid diseases (AITD) are common autoimmune disorders. A few studies have analyzed the association between serum vitamin D levels and AITD, and available data remain inconclusive.

The aim of this study was to evaluate the association between serum vitamin D levels and 3 types of AITD, that is Graves' disease (GD), Hashimoto's thyroiditis (HT), and postpartum thyroiditis (PPT).

Two independent case-control studies were designed. The first is a cross-sectional case-control study in which we examined the levels of 25(OH)D in patients with newly diagnosed GD or HT and in controls; the second is a nested case-control study in which we compared 25(OH)D levels in 610 women who developed PPT during the follow-up after delivery and those who did not.

Compared with the controls, GD patients and HT patients had significantly lower 25(OH)D levels. PPT cases also had a lower serum 25(OH)D concentration than controls. Serum 25(OH)D levels were associated with neither antithyroid peroxidase antibody nor antithyroglobulin antibody in GD and HT. There was no significant relationship between thyroid-stimulating hormone and 25(OH)D levels. Every 5 nmol/L increase in serum 25(OH)D concentrations was associated with a 1.55-, 1.62-, and 1.51-fold reduction in GD, HT, and PPT risk, respectively.

We observed a lower serum vitamin D levels in AITD patients compared with controls. The lower the vitamin D level is, not vitamin D deficiency per se, the higher the risk for developing AITD will be. However, vitamin D does not have strong association with the titers of thyroid antibodies or the levels of thyroid hormones.