Association between vitamin D receptor gene polymorphisms and Graves’ disease: a systematic review and meta-analysis

Purpose The pathogenesis of Graves’ disease (GD) and orbitopathy (GO) is not completely elucidated. On the other hand, vitamin D receptor (VDR) gene polymorphisms have been associated with vulnerability to a plethora of chronic autoimmune diseases. The primary aim of this study was to synthesize evidence on the association between VDR gene polymorphisms and GD. Secondary aim was to investigate their association with GO. Methods A comprehensive search was conducted in PubMed, CENTRAL and Scopus, up to December 8, 2018. Data were expressed as odds ratio (OR) with 95% confidence intervals (CI). Heterogeneity was quantified with I 2 index. Results Ten studies were included in the qualitative and quantitative analysis. TT subtype of TaqI polymorphism was associated with an increased risk of GD compared with Tt and tt polymorphisms (OR: 1.42; 95% CI, 1.05–1.94, p = 0.025), whereas tt was associated with a lower risk of GD, compared with TT and Tt polymorphisms (OR: 0.79; 95% CI, 0.62-0.99, p = 0.043). No association was found for ApaI, BsmI, and FokI polymorphisms. The bb subtype of BsmI polymorphism was associated with a lower risk in Asian, but with a higher GD risk in Caucasian populations, compared with BB/Bb subtypes. No eligible study was found regarding the association between VDR gene polymorphisms and the risk of GO. Conclusions The TT subtype of the TaqI polymorphism was associated with a higher susceptibility for GD compared with Tt and tt. Regarding BsmI, the bb subtype was associated with increased GD risk in Caucasians, whereas it is protective in Asians.