Anti-thyroid autoantibodies

Antithyroid autoantibodies (or simply antithyroid antibodies) are autoantibodies targeted against one or more components on the thyroid. The most clinically relevant anti-thyroid autoantibodies are anti-thyroid peroxidase antibodies (anti-TPO antibodies, TPOAb), thyrotropin receptor antibodies (TRAb) and thyroglobulin antibodies (TgAb). TRAb's are subdivided into activating, blocking and neutral antibodies, depending on their effect on the TSH receptor. Anti-sodium/Iodide (Anti–Na+/I−) symporter antibodies are a more recent discovery and their clinical relevance is still unknown. Graves' disease and Hashimoto's thyroiditis are commonly associated with the presence of anti-thyroid autoantibodies. Although there is overlap, anti-TPO antibodies are most commonly associated with Hashimoto's thyroiditis and activating TRAb's are most commonly associated with Graves' disease. Thyroid microsomal antibodies were a group of anti-thyroid antibodies, they were renamed after the identification of their target antigen (TPO).Anti-thyroid antibodies can be subdivided into groups according to their target antigen.The production of antibodies in Graves' disease is thought to arise by activation of CD4+ T-cells, followed by B-cell recruitment into the thyroid. These B-cells produce antibodies specific to the thyroid antigens. In Hashimoto's thyroiditis, activated CD4+ T-cells produce interferon-γ, causing the thyroid cells to display MHC class II molecules. This expands the autoreactive T-cell repertoire and prolongs the inflammatory response.The presence of anti-thyroid antibodies is associated with an increased risk of unexplained subfertility (odds ratio 1.5 and 95% confidence interval 1.1–2.0), miscarriage (odds ratio 3.73, 95% confidence interval 1.8–7.6), recurrent miscarriage (odds ratio 2.3, 95% confidence interval 1.5–3.5), preterm birth (odds ratio 1.9, 95% confidence interval 1.1–3.5) and maternal postpartum thyroiditis (odds ratio 11.5, 95% confidence interval 5.6–24).In 1912 Hakaru Hashimoto described hypothyroidism and goiter associated with thyroid lymphoid infiltration. In 1956 the anti-Tg antibody was detected in similar cases, elucidating the autoimmune cause of these characteristics. Later the same year, activating TSH receptor antibodies were discovered. Thyroid microsomal antibodies were discovered in 1964, which were subsequently renamed anti-TPO antibodies due to the identification of their autoantigen.