Low vitamin d status is associated with hypothyroid hashimoto’s thyroiditis

Abstract

OBJECTIVE: The association of low vitamin D status with autoimmune thyroid disease (AITD), which includes Hashimoto’s thyroiditis (HT) and Graves’ disease (GD), is controversial. The aim of this study was to investigate the correlation between vitamin D insufficiency and AITD, HT, and GD. DESIGN: Our cross-sectional study included patients who visited a tertiary hospital for thyroid evaluation or follow-up. A total of 776 patients in whom serum 25-hydroxyvitamin D [25 (OH) D], thyroid function, and anti-thyroid antibodies had been measured were analyzed retrospectively. Vitamin D insufficiency was defined as serum 25 (OH) D level <75 nmol/L. RESULTS: The prevalence of vitamin D insufficiency was significantly higher in the 369 patients with AITD than in the 407 without AITD (46.1% vs. 37.1%, p=0.011), and higher in the 221 patients with HT than in those with GD or non-AITD (48.9% vs. 41.9%, 37.1%, p=0.017). Among HT cases, patients with overt hypothyroidism had a significantly higher prevalence of vitamin D insufficiency (60.4% vs. 44.1%, 21.7%, 37.1%, respectively, p <0.001) and lower 25 (OH) D levels (80.1 ± 47.7 vs. 99.34 ± 61.2, 110.3 ± 69.9, 99.6 ± 53.7 nmol/L, respectively, p=0.009) compared with those with euthyroidism and subclinical hypothyroidism or those without AITD. Serum 25 (OH) D levels were significantly negatively correlated with serum thyroid stimulating hormone (TSH) levels after adjustment for age, sex, body mass index, and sampling season (r=-0.127, p=0.013). CONCLUSION: Vitamin D insufficiency was associated with AITD and HT, especially overt hypothyroidism. Low serum vitamin D levels were independently associated with high serum TSH levels.