Interpretation of Thyroid Autoantibodies in Hyperthyroidism

Abstract

Thyrotoxicosis is a clinical state with a variety of various etiologies that results from excess thyroid hormones, including hyperthyroidism and thyroiditis. Graves' disease (GD) is a well-known autoimmune thyroid disease that causes hyperthyroidism, and its pathogenesis is mainly driven by the thyroid-stimulating hormone receptor antibody (TSHRAb), which is highly specific for GD. Measuring the TSHRAb is a fast and accurate diagnostic tool for GD and has been used to monitor disease activity and the treatment response. However, conventional TSH-binding inhibitory immunoglobulin (TBII) does not differentiate between stimulating, blocking, or neutral antibodies. In contrast, thyroid stimulatory immunoglobulin bioassays differentiate between stimulating and blocking antibodies and have comparably high sensitivity and specificity to TBII for GD. We also discuss the role of thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) in thyrotoxicosis, although they are less specific than TSHRAb for GD. TPOAb is associated with autoimmune thyroiditis, while TgAb appears with TPOAb in patients with autoimmune thyroid disease. In addition, TPOAb or TgAb may be associated with a low recurrence of GD after discontinuing anti-thyroid drugs. Clinicians should interpret thyroid autoantibodies in the context of the patient's clinical presentation and consider their implications to manage and monitor thyrotoxicosis.