Micronuclei induction by I-131 exposure: Study in hyperthyroidism patients

To evaluate the eventual genetic damage induced by therapeutic exposure to I-131, We have studied the presence of micronuclei (MN) in binucleated peripheral blood lymphocytes from a group of 28 hyperthyroidism patients who received I-131 sodium iodide, via oral administration. The study was conducted over time and blood samples were obtained before the treatment, and 1 week, 1 month and 3 months after it. The results obtained indicate a positive relationship between dose and BNMN frequency as calculated by the linear regression coefficient, showing significant increases in the frequency of MN and BNMN (binucleated cells with MN) in the subgroup of patients that received more than 500 MBq. Taking into account that the patients studied were treated with relatively low doses of I-131, our positive results support the view that the MN assay is sensitive enough to monitor the chromosome damage resulting from the exposure.