RESUMO
BACKGROUND: The cause of autoimmune thyroid diseases (AITD), including Graves disease and Hashimotos thyroiditis, is largely unknown. To identify the genes responsible, most attention has been focussed on the HLA regions in the early studies. However, these studies have repeatedly shown a weak association between AITD and the HLA-DR3 in Caucasians. To understand and find out the mechanisms underlying the development of AITD, a search for non-HLA linked susceptibility genes is important. A recent study from American population have indicated an association between a polymorphism of CILA-4 gene and Graves disease. To clarify the relationship of the CTLA-4 polymorphism and AITD, the allele frequency of CTLA-4 gene from the patients with Graves disease and with Hashimotos thyroiditis in Korean papulation were analysed. METHODS: The CTLA-4 exon 1 polymorphism (49, A/G) was analysed by PCR-based, RFLP (Restriction Fragment Length Polymorphism) from 92 women and 37 men with Graves disease and 50 women and 9 men with Hashimotos thyroiditis diagnosed. Also, 287 healthy controls including 155 women and 132 men with no clinical evidence or family history of thyroid disease were enrolled. RESULTS: 1) In the group of Graves disease, there was significantly more patients with alanine homozygote (GG) than in control group (P<0.0005, RR=1.40). However, there was not significant with threonine homozygote (AA) between two groups (P=0.052). In the group of Hashimotos thyroiditis, no significant differences were found between all homozygotes and heterozygote. 2) In the group of Graves disease, there were significantly more patients with alanine homozygote (GG) (P<0.0001, RR=1.85) and significantly fewer patients with threonine homozygote (AA) than in the group of Hashimoto's thyroiditis (P<0.005, RR 0.25). CONCLUSION: Regardless of sex difference, alanine homozygote (GG) at exon 1 (codon 17) of CTLA-4 is associated with Graves disease in Korean population, which suggests genetic susceptibility is some role in the pathogenesis of Graves disease.