TPO and hypothyroidism: Autoimmune thyroid diseases present as hypothyroidism or hyperthyroidism, mainly depending on different types of plasma autoantibodies: hypothyroidism is often accompanied by thyroid peroxidase antibodies (TPO Abs) or thyroglobulin antibodies (Tg Abs); hyperthyroidism is often associated with the presence of thyroid-stimulating hormone receptor (TSH) antibodies.