Association between Vitamin D Receptor Gene Polymorphism (Fok 1), Vitamin D Status and Autoimmune Thyroiditis

Autoimmune thyroiditis gradually destroys the thyroid gland leading to hypothyroidism and may even lead to papillary thyroid carcinoma. Deficiency of Vitamin D has been linked to development of autoimmunity. Single nucleotide polymorphisms of the Vitamin D receptor gene have associated with autoimmune diseases in several studies. In this hospital based non interventional cross-sectional study Vitamin D receptor gene was studied for FokI (rs2228570) polymorphism from purified DNA in forty-eight adult cases and fifty age and sex matched healthy controls. This study was conducted in the department of Biochemistry, Calcutta National Medical College, Kolkata, West Bengal, India from January 2021 to July 2022. Their DNA was isolated using phenol chloroform method and were analysed for the related single nucleotide polymorphism by restriction digestion using appropriate restriction enzymes after amplification by PCR. Differences in allele frequencies between two groups were estimated by chi square and odds ratio test. Any potential association between the vitamin D anti TPO antibody and thyroid hormone status with polymorphic variations were assessed by post hoc ANOVA among the three genotypes. The distribution of FF genotype was significantly higher among the case group (Χ²=10.2788, p=0.006). The odds ratio for the allele F was significantly higher in case group for a range of 1.97 to 5.94 for 95 percent confidence interval (Χ²=13.9678, p=<0.001). The genotype FF group had significantly lowest Vitamin D (p=0.008) and highest Anti TPO ab (p=0.031) compared to Ff and ff genotypes. Thus, significant association was revealed between the VDR gene Fok1(rs2228570) polymorphism and autoimmune thyroiditis with the predominance of FF genotype being a strong susceptibility factor for autoimmune thyroiditis and Vitamin D deficiency in the studied population of Eastern India.