Furthermore, since an active iodide transport to the follicular cells is a critical step in thyroid hormone biosynthesis [20–22] and there is some evidence that NIS expression in thyroid tissue reflects the level of thyroid hormone production [23], decreased sodium iodide symporter expression seems to be an essential factor in the development of hypothyroidism in the patients with AITD. The gene discussed is TG; the disease is hypothyroidism.