What are thyroid antibodies, and how do they relate to thyroid function tests?

Thyroid antibodies are proteins produced by the immune system that mistakenly attack the thyroid gland. The presence of these antibodies indicates an autoimmune thyroid disorder. There are two main types: thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb). High levels of these antibodies are commonly associated with Hashimoto’s disease (hypothyroidism) and Graves’ disease (hyperthyroidism). In conjunction with a thyroid function test (TFT), checking for thyroid antibodies can help diagnose autoimmune thyroid conditions and guide treatment. Antibody tests are particularly useful when thyroid function tests show borderline or unexplained abnormal results.