When is thyroid antibody testing recommended and which antibodies should be tested?

From the Guidelines

Thyroid antibody testing is recommended for individuals with type 1 diabetes, particularly soon after diagnosis, and should include testing for antithyroid peroxidase and antithyroglobulin antibodies. This is based on the evidence that autoimmune thyroid disease is the most common autoimmune disorder associated with diabetes, occurring in 17–30% of patients with type 1 diabetes 1. The presence of thyroid autoantibodies is predictive of thyroid dysfunction, most commonly hypothyroidism, and can be identified through testing for antithyroid peroxidase and antithyroglobulin antibodies.

Key Points to Consider

• Testing for thyroid antibodies is important in patients with type 1 diabetes, as it can help identify those at risk for thyroid dysfunction 1.
• Antithyroid peroxidase antibodies are more predictive of thyroid dysfunction than antithyroglobulin antibodies in multivariate analysis 1.
• Thyroid function tests may be misleading if performed at the time of diagnosis due to the effects of previous hyperglycemia, ketosis, or ketoacidosis, and should be repeated after a period of metabolic stability and good glycemic control 1.
• The presence of thyroid antibodies indicates an autoimmune process that can lead to inflammation and dysfunction of the thyroid gland, and results should be interpreted in the context of clinical presentation and other thyroid function tests.

Recommendations for Testing

• Testing for antithyroid peroxidase and antithyroglobulin antibodies is recommended soon after diagnosis of type 1 diabetes 1.
• Thyroid-stimulating hormone concentrations should be measured at diagnosis when clinically stable or soon after glycemic control has been established, and repeated every 1–2 years or sooner if symptoms suggestive of thyroid dysfunction occur 1.
• Patients with previously normal TSH levels may be rechecked every 1–2 years or obtained at any time the growth rate is abnormal 1.

From the Research

Thyroid Antibody Testing Reasons

Thyroid antibody testing is recommended in several situations, including:

• Diagnosing autoimmune thyroid disease (AITD) such as Hashimoto's thyroiditis and Graves' disease 2, 3
• Identifying individuals at a higher risk of progression to hypothyroidism 2, 3
• Predicting the risk of fetal and neonatal thyroid dysfunction 3
• Guiding the management of thyrotoxicosis and Graves' orbitopathy 3
• Monitoring the treatment of autoimmune thyroid disease 2, 3

Thyroid Antibodies to be Tested

The following thyroid antibodies should be tested:

• Thyroid-stimulating hormone (TSH) receptor antibody (TRAb) to diagnose Graves' disease and predict the risk of fetal and neonatal thyroid dysfunction 3
• Anti-thyroid peroxidase antibodies (TPOAb) to identify individuals at a higher risk of progression to hypothyroidism and diagnose immune thyroiditis and Hashimoto's encephalopathy 3
• Anti-thyroglobulin antibodies (TgAb) to indicate thyroid autoimmunity and guide differentiated thyroid cancer treatment 3, 4
• Antinuclear antibody (ANA) and anti-DNA antibodies to determine the frequency of autoantibodies in autoimmune thyroid disease 5

Clinical Significance of Thyroid Antibodies

Thyroid antibodies have significant clinical implications, including:

• Elevated TgAb levels are associated with symptom burden in Hashimoto's thyroiditis patients, suggesting a role of thyroid autoimmunity in clinical manifestations of the disease 4
• Positive TRAb test establishes the diagnosis of Graves' disease, while a negative result supports other possible aetiologies 3
• TPOAb and TgAb positivity defines the presence of thyroid autoimmunity and allows for identifying individuals with a higher risk of progression to hypothyroidism 2, 3