The relationship between CD40 gene 5′ untranslated region position _1 site C/T polymorphism and the relapse of Grave's disease after antithyroid withdrawal

To investigate the relationship between the C/T polymorphism in the CD40 gene position_1 site and the relapse of Grave's disease (GD) after antithyroid withdrawal in Han population from Qingdao Shandong, we analyzed 198 patients (including 80 GD initial onset patients, 84 early relapse and 34 late relapse patients, and 110 healthy controls) by polymerase chain reaction-restric- tion fragment length polymorphism (PCR-RFLP) for the genotype and allele frequencies. Significant differences were observed in CD40 gene between GD and control group (χ2 = 23.133, P = 0.000; χ2 = 13.372, P = 0.000). The CC genotype frequency was significantly higher in GD group than that in control (23.7% vs 11.8%); the TT genotype frequency was significantly lower in GD group than that in control (7.6% vs 26.4%); the C allele frequency was significantly higher in GD group than that in control (58.1% vs 42.7%). As for the gene frequency, significant differences were observed in CD40 genotype frequencies between GD onset and relapse group (χ2 = 7.926, P = 0.019). The TT genotype frequency was significantly lower in GD relapse group than that in onset (3.4% vs 13.8%). But the significant differences in allele frequencies were not observed (χ2 = 0.665, P = 0.415). Significant differences were also observed in CD40 gene genotype frequencies between GD early relapse and late relapse group (χ2 = 11.278, P = 0.004). However, the significant differences in allele frequencies were not observed (χ2 = 2.272, P = 0.099). All these results indicate that the polymorphism of C allele in CD40 gene position _1 site is associated with the susceptibility to the development and relapse of GD in Han population of Qingdao Shandong.