Autoimmune thyroid diseases and Helicobacterpylori： The correlation is present only in Graves＇s disease

AIM： To investigate the correlation between autoimmune thyroid diseases （ATDs） and the prevalence of Cag-A positive strains of Helicobacter pylori （H. pylori） in stool samples. METHODS： We investigated 112 consecutive Caucasian patients （48 females and 4 males with Graves＇ disease and 54 females and 6 males with Hashimoto＇ s thyroiditis HT）, at their first diagnosis of ATDs. We tested for H. pylori in stool samples using an amplified enzyme immunoassay and Cag-A in serum samples using an enzyme-linked immunoassay method （ELISA）. The results were analyzed using the two-sided Fisher＇ s exact test and the respective odds ratio （OR） was calculated. RESULTS： A marked correlation was found between the presence of H. pylori （P ≤ 0.0001, OR 6.3） and, in particular, Cag-A positive strains （P ≤ 0.005, OR 5.3）in Graves＇ disease, but not in Hashimoto＇s thyroiditis, where we found only a correlation with Cag-A strains （P ≤ 0.005, OR 8.73） but not when H. pylori was present. CONCLUSION： The marked correlation between H. pylori and Cag-A, found in ATDs, could be dependent on the different expression of adhesion molecules in the gastric mucosa.