Endocrine Abstracts

Introduction: Vitamin D is postulated to play a significant role in the immune system modulation and its deficiency has been reported in some autoimmune disorders. Polymorphisms of different vitamin D-related genes, among them vitamin D receptor gene (VDR), could either be a risk factor for autoimmune diseases. Therefore the aim of the study was to assess the association between VDR Cdx2 (rs11568820) polymorphism and autoimmune thyroid disease (AITD) among the Caucasian-Polish population.

Studied group: 272 subjects diagnosed with AITD (mean age 50.55) and 119 healthy age and sex matched controls. AITD group comprised of 166 patients with autoimmune thyroiditis (AIT) and 106 patients with thyroid associated orbitopathy (TAO) in the course of Graves’ disease. In the control group AITD and other autoimmune diseases or neoplasms were excluded.

Methods: Cdx2 polymorphism genotyping was performed with the use of real-time PCR with TaqMan probes, randomly selected samples were additionally analyzed by direct sequencing. The statistical significance of differences in allele and genotype distribution between AITD and controls, as well as in subgroups of AITD were evaluated by χ² or Fisher’s exact test, where appropriate. A P value of <0.05 was considered significant.

Results: Observed allele frequencies were in Hardy-Weinberg equilibrium, except of TAO subgroup. In both AITD and the control group G allele and GG homozygote predominated, as expected for Caucasian population. The observed allele and genotype frequencies did not differ significantly between AITD and controls (P=0.30 and P=0.56, respectively). When analyzing AIT vs. controls, differences in allele or genotype distribution were also not significant (P=0.41 and P=0.54, respectively). In TAO group frequency of genotype AA was higher comparing to controls (6.60% vs. 1.68%), but without statistical significance (P=0.09; OR =4.14; 95% CI: 0.89–19.96). We also analyzed TAO vs. AIT and found significantly higher AA homozygote in TAO group comparing to AIT (6.60% vs. 1.20%; P=0.03; OR =5.80; 95% CI: 1.25–27.9).

Conclusions: There is no statistically significant difference in allele or genotype distribution of VDR Cdx2 polymorphism between AITD and the control group and between AIT or TAO and the control group among the Caucasian-Polish population. However, we found that TAO patients differed significantly from AIT group in VDR Cdx2 genotype distribution.