TSH receptor antibodies – TRAb

The TSH receptor antibody (TRAb) analysis is an essential tool for doctors when diagnosing, monitoring, and treating autoimmune thyroid diseases. As a patient, it is important to understand the purpose of this test, as well as the significance of the results, to ensure the best possible care for your health. For more information, or if you have additional questions, consult your doctor or our expert team at IntroLab laboratory in Belgrade.

What are TSH receptor antibodies (TRAb)?

TSH receptor antibodies (TRAb) are a specific type of antibodies that are produced in the body as part of the immune response. These antibodies have the ability to bind to TSH receptors (Thyroid-Stimulating Hormone) on thyroid gland cells.

TSH receptors are part of the family of G-protein-coupled receptors with 7 transmembrane domains, similar to receptors for other glycoprotein hormones, such as LH and FSH. They are synthesized as large precursor molecules that are deposited in the cell membrane.

When TRAb antibodies bind to TSH receptors, they can mimic the action of TSH. This can result in either excessive or insufficient production of thyroid hormones, causing symptoms of hyper- or hypothyroidism. The production of these antibodies can be genetic, but it can also be caused by environmental factors.

When are TSH receptor antibodies (TRAb) examined?

TRAb analysis is a key tool in diagnosing and monitoring autoimmune thyroid diseases. This test is often ordered when there are symptoms or signs of thyroid dysfunction that suggest a possible autoimmune thyroid disease, such as Graves’ disease or Hashimoto’s disease.

In situations where the results of other thyroid function tests, such as TSH, T3, and T4 measurements, are unclear or contradictory, TRAb analysis can provide additional information. This analysis is particularly useful for monitoring the effects of therapy for Graves’ disease or for assessing the risk of developing Graves’ ophthalmopathy, especially in smoking patients. During antithyroid drug therapy for Graves’ disease, TRAb levels tend to decrease. Low levels or absence of TRAb after drug treatment can indicate disease remission, which may suggest the possibility of discontinuing therapy.

It is particularly important to note that TRAb analysis is recommended during the last trimester of pregnancy. Since TRAb antibodies are IgG class, they can cross the placenta and potentially cause neonatal thyroid disease. Therefore, measuring TRAb during pregnancy in patients with a history of thyroid disease is important for assessing the risk of thyroid disease in the newborn.

How are the results interpreted?

TRAb analysis results can be divided into decreased, normal, and elevated values.

• Decreased values: Decreased TRAb levels are usually not a cause for concern, as a healthy person should not produce these antibodies.
• Normal values: If TRAb levels are normal, it means there are no detected antibodies that would affect thyroid function.
• Elevated values: Elevated TRAb levels may indicate autoimmune thyroid diseases, such as Graves’ disease or Hashimoto’s disease.

The interpretation of TRAb analysis results depends on the overall clinical picture and should be interpreted in the context of other thyroid function tests and the patient’s symptoms.

Specificities and subtypes of analysis

In the diagnosis and monitoring of thyroid diseases, TRAb analysis is just one part of a broader spectrum of tests. These tests provide a comprehensive insight into thyroid function and can help in accurately determining the diagnosis and therapy. Here are some analyses that are often used in combination with TRAb analysis:

• TSH (thyroid-stimulating hormone): This test measures the level of the hormone produced by the pituitary gland that stimulates the thyroid gland to produce T3 and T4 hormones.
• T4 and FT4 (thyroxine and free thyroxine): These tests measure the level of T4 hormone in the blood. FT4 refers to the part of the T4 hormone that is not bound to proteins and can enter cells.
• T3 and FT3 (triiodothyronine and free triiodothyronine): These tests measure the level of T3 hormone in the blood. FT3 refers to the part of the T3 hormone that is not bound to proteins and can enter cells.
• Anti-TPO antibodies: This test measures the level of antibodies against the enzyme thyroid peroxidase (TPO), which plays a key role in the production of thyroid hormones.
• Anti-TG antibodies: This test measures the level of antibodies against thyroglobulin (TG), a protein produced by the thyroid gland that is essential for the production of T3 and T4 hormones.
• TG (thyroglobulin): This test measures the level of thyroglobulin in the blood, which can be elevated in some forms of thyroid disease.
• Calcitonin: This test measures the level of calcitonin, a hormone produced by the thyroid gland that helps regulate calcium levels in the blood.

Preparation for the test

No special preparation is required for the TSH receptor antibody (TRAb) analysis. Patients can continue with their usual daily activities and routines before testing. There are no specific dietary or lifestyle restrictions that need to be followed before going to the laboratory.