Vitamin D receptor gene FokI but not TaqI, ApaI, BsmI polymorphism is associated with Hashimoto’s thyroiditis: a meta-analysis

Four VD receptor (VDR) gene polymorphisms (TaqI, ApaI, FokI and BsmI) have been reported to influence Hashimoto's thyroiditis (HT) risk. However, individual studies have produced inconsistent results. We conducted a comprehensive meta-analysis of eleven case-control studies to better understand roles of the four polymorphisms in HT development. The results showed only FokI polymorphism was significantly associated with the risk of HT (F vs f: OR = 1.44, 95% CI = 1.09-1.91, P = 0.010; FF vs Ff + ff: OR = 1.72, 95% CI = 1.09-2.70, P = 0.019). Subgroup analyses demonstrated the significant effect was only present in Asian population (F vs f: OR = 1.45, 95% CI = 1.07-1.95, P = 0.016; FF vs ff: OR = 1.64, 95% CI = 1.03-2.59, P = 0.036; FF + Ff vs ff: OR = 1.34, 95% CI = 1.00-1.80, P = 0.047; FF vs Ff + ff: OR = 1.64, 95% CI = 1.03-2.64, P = 0.039), but not in Caucasian. For TaqI, ApaI and BsmI polymorphisms, no significant association was found in any model comparison. Based on the current literature, it appears that only VDR FokI polymorphism is associated with HT risk in Asian population, but not in Caucasians; and the TaqI, ApaI and BsmI polymorphisms have not positive association neither in the overall population, nor when stratified by ethnicity. Further well-designed studies with larger sample sizes and different ethnic population are needed to clarify the present findings.