Consecutive patients with thyroid diseases referred to the Isotopic Institute at the Rabin Medical Center, Campus Beilinson for either radioactive iodine (131I) thyroid scan or radioactive iodine (131I)treatment for their disease, will be tested, prior to the radioactive iodine, for H. pylori infection and CagA protein by serology. Patient with positive serology for H. pylori will be tested for active gastric infection using the H.pylori stool antigen test. The study population will include all patients who tested positive for H.pylori both on serology and stool antigen tests. Six to eight weeks and 6 month after administration of radioactive iodine (131I) , stool antigen or H.pylori will be tested again to confirm persistence of H.pylori eradication.