To find out if the clinical outcome is statistically related to the radio-sensitivity (both in terms of γ-H2AX and MN induction) before the I-131 treatment, a statistical test has been performed to evaluate the conditional probability of each of the three types of response (hypo-, eu-, hyper-thyroidism) given a certain level of radio-sensitivity before the treatment. This evidence concerns the gene H2AX and thyroid gland disorder.