From the Guidelines
Thyroid antibodies are proteins produced by the immune system that mistakenly attack the thyroid gland or its components, with the most common types being thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), which are associated with autoimmune thyroid conditions such as Hashimoto's thyroiditis and Graves' disease. These antibodies indicate an immune response against the thyroid gland, which can lead to thyroid dysfunction over time. The presence of thyroid antibodies, particularly TPOAb, has been shown to be predictive of thyroid dysfunction, with a study from Sweden indicating that TPOAb are more predictive than TgAb in multivariate analysis 1.
Types of Thyroid Antibodies
- Thyroid peroxidase antibodies (TPOAb)
- Thyroglobulin antibodies (TgAb)
- Thyroid-stimulating hormone receptor antibodies (TRAb)
Clinical Significance
Testing for thyroid antibodies helps diagnose autoimmune thyroid disorders, even before thyroid hormone levels become abnormal. People with positive antibody tests may need regular monitoring of thyroid function, as they have an increased risk of developing thyroid dysfunction over time. The presence of these antibodies reflects the body's immune system incorrectly identifying thyroid tissue as foreign and mounting an attack against it, which can gradually damage the thyroid gland and affect its ability to produce thyroid hormones. According to the most recent guidelines, patients with type 1 diabetes should be screened for thyroid peroxidase and thyroglobulin antibodies at diagnosis, and thyroid-stimulating hormone concentrations should be measured after metabolic control has been established 1.
Recommendations
- Screen for thyroid antibodies, particularly TPOAb and TgAb, in patients with type 1 diabetes at diagnosis
- Measure thyroid-stimulating hormone concentrations after metabolic control has been established
- Monitor thyroid function regularly in patients with positive antibody tests
- Consider screening for other autoimmune diseases, such as celiac disease, in patients with type 1 diabetes 1.
From the Research
Thyroid Antibodies
Thyroid antibodies are proteins produced by the immune system that attack the thyroid gland, leading to autoimmune thyroid disease (AITD) [ 2 ]. The most common types of thyroid antibodies are:
- Anti-thyroid peroxidase antibodies (TPOAb)
- Anti-thyroglobulin antibodies (TgAb)
- Thyroid-stimulating hormone receptor antibodies (TRAb)
Role of Thyroid Antibodies
Thyroid antibodies play a crucial role in the diagnosis and management of thyroid diseases, including:
- Graves' disease (GD)
- Hashimoto's thyroiditis (HT)
- Thyrotoxicosis
- Hypothyroidism TRAb testing is essential in diagnosing GD and guiding clinical management decisions [ 3 ]. TPOAb and TgAb indicate thyroid autoimmunity and aid in the diagnosis of immune thyroiditis and Hashimoto's encephalopathy [ 3 ].
Prevalence and Associations
The prevalence of AITD is estimated to be 5%, with an even higher prevalence of antithyroid antibodies [ 4 ]. Associations exist between AITD and other organ-specific or systemic autoimmune disorders, such as polyglandular autoimmune syndromes, Sjögren's syndrome, and rheumatoid arthritis [ 4 ]. Additionally, studies have shown an association between AITD and papillary thyroid cancer [ 4 ].
Mechanisms and Pathogenesis
The mechanisms that trigger the autoimmune attack on the thyroid are still under investigation [ 4 ]. Epidemiological data suggest an interaction between genetic susceptibility and environmental triggers, leading to the breakdown of tolerance and the development of disease [ 4 ]. Cytokines and chemokines play a crucial role in the pathogenesis of AITD, with T helper 1 (Th1) lymphocytes responsible for enhanced IFN-γ and TNF-α production [ 4 ].