Hypothyroidism represents the most frequent thyroid-related effect in patients treated with RT for head and neck cancers (20%–30%), but in clinical practice the dose to the thyroid gland and pre- and posttreatment levels of thyroid hormones have not yet been assessed.5 In our analysis, the incidence of hypothyroidism evaluated after adjuvant therapy (RT and concurrent RT-CT) was 21.5%, which is comparable with the results of historical series, i.e. in the range 20%–30%.4 This evidence concerns the gene TG and thyroiditis.