What type of antibodies are typically positive in Hashimoto's thyroiditis?

In Hashimoto's thyroiditis, the immune system produces antibodies that target thyroid proteins, leading to autoimmune thyroid gland destruction. The antibodies most commonly associated with Hashimoto's thyroiditis are anti-thyroid peroxidase (anti-TPO) antibodies.

Anti-TPO antibodies are directed against the enzyme thyroid peroxidase, which plays a critical role in the synthesis of thyroid hormones by catalyzing the iodination of tyrosine residues in thyroglobulin. The presence of these antibodies indicates an autoimmune attack on the thyroid and is a hallmark of Hashimoto's thyroiditis. Many patients with the condition test positive for anti-TPO antibodies, and their levels can correlate with disease activity and severity.

Although anti-thyroglobulin (anti-TG) antibodies can also be present in Hashimoto's thyroiditis, they are less specific than anti-TPO antibodies for this condition. Other antibody types, such as anti-TSH receptor antibodies, are more associated with conditions like Graves' disease, while anti-T4 antibodies do not exist in a clinical context. Therefore, anti-TPO antibodies are usually considered the primary indicators in diagnosing and understanding Hashimoto's thyroiditis.