Loss of immune tolerance, reactivity to thyroid autoantigens—circulating thyroid peroxidase (TPO) and thyroglobulin (TG) antibodies (Ab), mainly in HT, and thyroid-stimulating hormone receptor (TSHR)Ab as the hallmark of GD—and infiltration of the thyroid by T and B lymphocytes, which ultimately drive the cytokine production, are the major determinants of AITD [8,9]. This evidence concerns the gene TPO and hematocrit.