From the Guidelines
TPO antibodies are more predictive than thyroglobulin antibodies for autoimmune thyroid disease, particularly in diagnosing Hashimoto's thyroiditis, as indicated by a study from Sweden in multivariate analysis 1. The difference between Thyroid Peroxidase (TPO) antibody and Thyroglobulin (TG) antibody lies in their diagnostic purposes and sensitivities.
- TPO antibodies are more sensitive and specific for diagnosing Hashimoto's thyroiditis, present in about 90-95% of patients with this condition.
- Thyroglobulin antibodies are less sensitive, appearing in only 60-70% of Hashimoto's patients, but can be useful when TPO antibodies are negative despite clinical suspicion of autoimmune thyroid disease. For comprehensive thyroid autoimmunity assessment, both antibodies should be tested together, especially in cases of unexplained hypothyroidism or goiter.
- TPO antibodies target the enzyme essential for thyroid hormone production,
- while thyroglobulin antibodies attack the protein that stores thyroid hormones, explaining their different sensitivities and clinical implications in autoimmune thyroid conditions. The presence of either antibody during pregnancy requires close monitoring as they can cross the placenta and affect fetal thyroid function, and high levels of TPO antibodies can predict progression from subclinical to overt hypothyroidism 1. In the context of type 1 diabetes, autoimmune thyroid disease is the most common autoimmune disorder associated with diabetes, occurring in 17–30% of individuals with type 1 diabetes, and the presence of thyroid autoantibodies is predictive of thyroid dysfunction—most commonly hypothyroidism, although hyperthyroidism occurs in 0.5% of people with type 1 diabetes 1.
From the Research
Difference between Thyroid Peroxidase (TPO) antibody and Thyroglobulin (TG) antibody
- TPO antibody and TG antibody are two types of autoantibodies associated with autoimmune thyroid disease (AITD) 2, 3, 4, 5, 6
- TPO antibody is the primary enzyme involved in thyroid hormonogenesis and is present on the apical surface of thyroid follicular cells 2, 4, 6
- TG antibody is directed against thyroglobulin, a protein produced by the thyroid gland 3, 4, 6
- TPO antibodies are capable of inducing antibody-dependent cell-mediated cytotoxicity, whereas TG antibodies are not 2
- TPO antibodies are more closely involved in cell-mediated cytotoxicity and are the hallmark of AITD, present in almost all patients with Hashimoto's thyroiditis and in 75% of patients with Graves' hyperthyroidism 2
- TG antibodies are also present in AITD, but their role is less clear, and they are often used as a marker of thyroid autoimmunity 3, 4, 6
- The epitope specificity of TPO antibodies can vary between patients with different thyroid autoimmune diseases, such as Graves' disease and Hashimoto's thyroiditis 5
- The measurement of TPO and TG antibodies can be useful in the diagnosis and management of AITD, including the investigation of goitre, diagnosis of Graves' and Hashimoto's disease, and prediction of risk of developing hypothyroidism 3, 6