The effects of vitamin D and gene polymorphisms on susceptibility to thyroid peroxidase antibody positivity.

Background: The etiology of Hashimoto's thyroiditis (HT) involves genetic and environmental factors. There is a lack of clarity regarding the relationship between Vitamin D and HT. This study aimed to investigate the effect of Vitamin D and gene polymorphisms on thyroid peroxidase antibody (TPOAb) positivity.

Methods: A total of 9,966 participants were included from a survey conducted in East China from 2014 to 2016. We measured the levels of 25(OH)D, thyroid hormones and autoimmune antibodies. rs11675434, rs9277555, and rs301799 were genotyped. Based on these 3 SNPs, a weighted genetic risk score was calculated for TPOAb.

Results: The proportion of females in the TPOAb-positive group was greater than that in the TPOAb-negative group (74.2% vs. 57.2%, P<0.001). Vitamin D levels were lower in the TPOAb-positive group than in the TPOAb-negative group (40.07±11.87 vs. 40.80±12.84, P=0.01). The GG genotype of rs9277555 and the TT genotype of rs11675434 were correlated with the risk of TPOAb positivity (OR=1.34, 95% CI 1.13-1.59, P=0.001; OR=1.29, 95% CI 1.06-1.58, P=0.01). TPOAb-GRS was associated with TPOAb positivity (OR=3.17, 95% CI 1.72-5.84; P<0.001). When stratified by Vitamin D group, the association between TPOAb-GRS and TPOAb positivity existed only in the Vitamin D deficiency group (OR=3.41, 95% CI 1.73-6.70 P<0.001) but not in the control group (OR=2.45, 95% CI 0.59-10.19, P=0.22).

Conclusions: This study suggested that TPOAb-GRS was associated with TPOAb positivity in the Han Chinese population, mainly due to rs9277555 and rs11675434. The hereditary effect of TPOAb positivity differed depending on Vitamin D status.