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The association between cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) exon-1 +49 A/G polymorphism and Hashimoto's thyroiditis (HT) has been widely studied. The results, however, are mixed. This study provides a comprehensive evaluation of the relationship between the genetic risks of CTLA-4 +49 A/G polymorphism and HT. A meta-analysis was conducted in over 4,600 subjects included in 18 case-control studies that were published up to November 15th, 2012. Our meta-analysis indicated that the CTLA-4 genotype was associated with the risk of HT in the allele comparison, homozygote comparison, heterozygote comparison, the dominant genetic model and the recessive genetic model. In the dominant genetic model, variant G allele carriers (GG + GA) of CTLA-4 +49 A/G polymorphism increased the risk of HT comparing to the homozygote AA [odds ratio (OR) = 1.70, 95% confidence interval (CI) 1.37-2.12 for GG + AG vs. AA]. The analysis by ethnicity groups suggested that Asian population (OR = 2.13, 95% CI 1.48-3.07 for GG + AG vs. AA) and Caucasian population (OR = 1.47, 95% CI 1.13-1.91 for GG + AG vs. AA) had significant increased HT risks. The association remained significant after adjusting for publication bias using the trim and fill method. Sensitivity analysis showed that the results were less stable, suggesting that these results should be explained with caution. In summary, this meta-analysis suggested that CTLA-4 +49 A/G polymorphism may be a risk factor for HT.

Graves' disease (GD) and Hashimoto's thyroiditis (HT) are both common autoimmune diseases of the thyroid gland (AITD). The IL-4 is involved in both humoral and cellular immunity. The aim of this study was to test whether the IL-4 gene could be used as a genetic marker to predict the development of AITD amongst the Chinese population of Taiwan. For this study, a normal control group of 105 healthy subjects and two experimental groups featuring individuals afflicted with either GD (104 patients) or HT (109 patients) were examined. Polymerase chain reaction (PCR) was used to analyze the variable number of tandem repeats (VNTRs) polymorphism for the IL-4 gene intron 3 and PCR-based restriction analysis using endonuclease BsmFI was undertaken for the same gene at the promoter -590 position. We found no significant difference in the frequencies of presence of genotype and allelic variants for the IL-4 gene at both the intron 3 and the promoter regions between the normal control group and each of the two patient groups. These findings suggest that the IL-4 gene polymorphisms that arise at either intron 3 or promoter -590 positions are not suitable genetic markers for AITD among Taiwanese Chinese.