From the Guidelines
Thyroid antibodies are proteins produced by the immune system that target components of the thyroid gland, indicating autoimmune thyroid disease, and the most recent evidence suggests that antithyroid peroxidase antibodies are more predictive than antithyroglobulin antibodies in multivariate analysis 1.
Definition and Types of Thyroid Antibodies
Thyroid antibodies are proteins produced by the immune system that target components of the thyroid gland, indicating autoimmune thyroid disease. The most common thyroid antibodies tested include:
- Thyroid peroxidase antibodies (TPOAb)
- Thyroglobulin antibodies (TgAb)
- Thyroid-stimulating hormone receptor antibodies (TRAb) These antibodies are associated with autoimmune thyroid disorders like Hashimoto's thyroiditis or Graves' disease.
Clinical Significance and Testing
Testing for these antibodies is recommended when autoimmune thyroid disorders are suspected, particularly in patients with:
- Abnormal thyroid function tests
- Goiter
- Symptoms of hypo/hyperthyroidism The presence of TPOAb or TgAb suggests Hashimoto's thyroiditis, while TRAb indicates Graves' disease.
Diagnosis and Treatment
These tests require a simple blood draw and results typically return within a few days. Positive antibody results help confirm diagnosis and guide treatment decisions, though treatment is primarily based on thyroid hormone levels rather than antibody levels.
Monitoring and Prognosis
Antibody levels may remain elevated even after treatment and don't necessarily require regular monitoring once diagnosis is established. The development of thyroid antibodies reflects a breakdown in immune tolerance where the body mistakenly identifies thyroid tissue as foreign, leading to inflammation and eventual thyroid dysfunction, as noted in a study from Sweden 1.
Key Points to Consider
- Autoimmune thyroid disease is the most common autoimmune disorder associated with diabetes, occurring in 17–30% of patients with type 1 diabetes 1.
- At the time of diagnosis, about 25% of children with type 1 diabetes have thyroid autoantibodies, which is predictive of thyroid dysfunction, most commonly hypothyroidism, although hyperthyroidism occurs in ~0.5% of patients with type 1 diabetes 1.
- Thyroid function tests may be misleading if performed at the time of diagnosis due to the effect of previous hyperglycemia, ketosis or ketoacidosis, weight loss, etc., and should be repeated soon after a period of metabolic stability and good glycemic control 1.
From the Research
Definition and Types of Thyroid Antibodies
- Thyroid antibodies, also known as thyroid autoantibodies, are antibodies that target the thyroid gland and can cause autoimmune thyroid diseases such as Hashimoto's disease and Grave's disease 2.
- There are several types of thyroid antibodies, including:
- TgAb (thyroglobulin antibodies): antibodies against thyroglobulin, a protein produced by the thyroid gland 2, 3.
- TPOAb (thyroid peroxidase antibodies): antibodies against thyroid peroxidase, an enzyme involved in thyroid hormone production 2, 4.
- TSH receptor antibodies: antibodies that target the TSH receptor, which can stimulate or block the production of thyroid hormones 2, 4, 5, 6.
- Anti-TPO (antimicrosomal antibodies): antibodies against thyroid peroxidase, which can be involved in the destruction of thyroid tissue 3.
- Anti-Tg (antithyroglobulin antibodies): antibodies against thyroglobulin, which can be involved in the destruction of thyroid tissue 3.
Clinical Significance of Thyroid Antibodies
- Thyroid antibodies can be used as diagnostic markers for autoimmune thyroid diseases such as Hashimoto's disease and Grave's disease 2, 4, 3.
- The presence of thyroid antibodies can also be associated with an increased risk of recurrence of hyperthyroidism in patients with Grave's disease 6.
- The levels of thyroid antibodies can be influenced by treatment with antithyroid drugs, such as methimazole, and thyroid hormone replacement therapy 4, 5, 6.