Thyroperoxydase (TPO) is an enzyme required to convert iodine into a special compound that binds to thyroglobulin to form hormones of thyroid glands - T3, T4. Antibodies are components of the immune system that destroy any molecules foreign to the body. It is still not known exactly why immunity fails when antibodies to one's own organs start to be produced.

Thus, the body begins to destroy TPO itself and, as a consequence, the amount of hormones T3, T4 produced decreases (manifested as hypothyreosis). In addition, when antibodies come into contact with TPO, immune complexes are formed, which settle on the walls of the thyroid gland and cause its inflammation - autoimmune thyroiditis. Inflammation leads to the fact that from the destroyed structures of the gland in the blood comes a large amount of T3, T4 - which gives the clinical picture of hyperthyroidism. Antibodies are able to pass through the placenta from mother to fetus and negatively affect the development of the child.

The test has good specificity and is detected in 95% of patients with Hashimoto's thyroiditis