Pragmatic Use of Thyroid Autoantibodies in Clinical Practice: An Update.

Autoimmune thyroid diseases, encompassing Hashimoto's thyroiditis and Graves' disease, are driven by immune-mediated targeting of thyroid antigens. Central to their diagnosis and management is the detection of circulating thyroid autoantibodies (TAbs), particularly those against thyroid peroxidase (TPO), thyroglobulin (Tg) and the thyrotropin receptor (TR). These antibodies have traditionally served as disease markers, but emerging evidence underscores their functional roles in pathogenesis, prognostication and therapeutic decision-making. For example, TR antibodies not only confirm the diagnosis of Graves' disease but also help assess disease activity, predict treatment response and evaluate foetal risk during pregnancy. Similarly, TPO and Tg antibodies contribute to the identification of subclinical thyroid dysfunction and have implications for reproductive health and immune-related adverse events from biologic therapies. Newly identified antibodies targeting molecules, such as pendrin, sodium-iodide symporter and megalin, suggest a broader autoimmune footprint than previously recognized. However, their clinical relevance remains to be fully elucidated. The interpretation of TAb is further complicated by assay variability, dynamic antibody titres and their presence in euthyroid individuals, particularly in special populations such as pregnant women, children and those with other autoimmune disorders. This article synthesizes current insights into the immunological basis, diagnostic performance and clinical applications of TAb. It emphasizes the need for a pragmatic, context-specific approach to testing, advocating for a more tailored integration of antibody data into clinical decision-making. By aligning immunologic knowledge with real-world practice, this article aims to refine the utility of TAb in contemporary endocrine care.