HT represents a T-cell-mediated autoimmune disease characterized by goiter, presence of circulating anti-thyroid peroxidase (TPOAb) and/or anti-thyroglobulin (TgAb) antibodies, and intrathyroidal infiltration of B and T cells with a CD4+ Th1 predominance [46,63]. The gene discussed is CD4; the disease is hematocrit.