Thesis & Dissertations

Introduction: The calcitriol receptor, also known as vitamin D receptor (VDR) is a transcription factor. Upon activation by vitamin D, the VDR forms a heterodimer with the retinoid-X receptor and binds to hormone response elements on DNA resulting in transcription of specific gene products.VDR polymorphisms have been associated with some autoimmune diseases including Hashimoto thyroiditis and Grave’s disease. Hashimoto thyroiditis is an inherited disorder that is characterized by the production of immune cells and auto-antibodies that can damage thyroid cells and compromise their ability to produce thyroid hormones. Hashimoto thyroiditis affects 2% of the general population. It is ten times more frequent in women than in men with people involved at ages of 30-50 years. It has been shown that gene polymorphism in VDR was associated with HT in some populations but was not investigated in a Lebanese population. Aim: This study was focused on investigating the association of VDR gene polymorphisms BsmI intron 8 and TaqI in exon 9 with susceptibility to Hashimoto thyroiditis in a Lebanese population. In addition, this study examined whether these SNPs are correlated with TSH and vitamin D levels in the blood of HT patients. Materials and Methods: Genotyping of BsmI and TaqI SNPs in the vitamin D receptor genewas performed in 70 Hashimoto patients and 80 control subjects. Genomic DNA extraction was obtained from venous blood samples, quantified and subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using specific primers and restriction enzymes for each polymorphism. Results: Studying the different genotypic frequency distribution of VDR BsmI and TaqI SNPs between Hashimoto patients and control subjects revealed no statistical significance with a P-value >0.05. Allelic frequency distribution in Hashimoto patients for the BsmI SNP frequency revealed 50% in the A or G allele, while that of controls was 42.5% for the A allele and 57.5% of the G allele (p-value=0.193). Whereas, the allelic frequency of the TaqI SNP in Hashimoto patients revealed 49.28% for the T allele and 50.71% for the C allele, the frequency in control subjects of the T allele was 55.6% and the C allele was 44.3% (p-value=0.272). There was no significant association between TSH levels and vitamin D levels with any of the VDR SNPs examined in this study (BsmI and TaqI). Conclusion: There was no association between the vitamin D receptor gene polymorphisms BsmI, TaqI, and incidence of Hashimoto thyroiditis, TSH or vitamin D levels in the studied Lebanese population.