Deciphering the results of thyroid blood tests can feel like trying to solve an intricate puzzle. One aspect of this puzzle that often receives much attention is the concern around thyroid antibodies. We frequently receive queries about what the presence of these antibodies signifies, whether these should be tested, and how often.
Thyroid Antibodies: What are they, and what do they signal?
Let's imagine antibodies as the body's security personnel. They're proteins that form in our blood when foreign invaders, known as antigens, attack. These could be harmful entities like bacteria or viruses. Now, picture thyroid antibodies as guards who are produced by the body’s immune system and mistakenly target the body's own thyroid cells as enemies, initiating an attack. Their misguided attack could lead to inflammation, damaging tissues, or creating disruptions in the thyroid's functioning. Such antibodies are found in autoimmune thyroid disorders like Hashimoto’s thyroiditis and Graves’ disease.
When thyroid tests show signs of a thyroid complication, and there's a clinical suspicion of autoimmune thyroid disease, one or more thyroid antibody tests may be ordered. These tests help confirm the diagnosis. It's not rare for some people to test positive for more than one type of thyroid antibody.
The existence of these antibodies in people with thyroid disease that is subclinical (meaning without obvious symptoms but tests show some thyroid hormonal imbalance) hints at the possibility of them developing a full-scale thyroid disease in the future. They can also be found in individuals without any thyroid disorder. Research by Engler, H., Riesen, W., & Keller, B. (1994) emphasizes the importance of efficient methods for TPO antibody detection, underscoring their critical clinical significance in diagnosing thyroid diseases.
The Different Types of Antibodies and What They Indicate
1. Thyroid Peroxidase Antibodies (TPOAb): Elevated in autoimmune thyroiditis, also known as Hashimoto’s thyroiditis, and occasionally may be increased in Graves’ disease. Studies have identified TPO as the antigen involved in autoimmune thyroid diseases (Portmann, L., Hamada, N., Heinrich, G., & Degroo, L. J., 1985; Czarnocka, B., Ruf, J., Ferrand, M., Carayon, P., & Lissitzky, S., 1985).
2. Thyroglobulin Antibodies (Tg Ab): These antibodies are directed against thyroglobulin, a protein present in the thyroid gland that helps produce thyroid hormones.
3. Thyroid Stimulating Hormone Receptor Antibodies (TSHR Ab, or TRAb): These antibodies can stimulate and block the thyroid gland and are notably raised in Graves’ disease.
4. Thyroid-Stimulating Immunoglobulin (TSI): Specific to Graves’ disease, this stimulatory antibody can cause overactivity in the thyroid gland.
The Role of the Thyroid Peroxidase Antibodies (TPOAb) Test
If TPO antibodies are detected in patients with a high TSH, it may mean that the cause of hypothyroidism is an autoimmune disease, such as Hashimoto’s thyroiditis. When they're not found, the high TSH may resolve spontaneously, or there could be a non-autoimmune thyroid disorder caused by other factors, such as viral infections, iodine deficiency, or certain medications.
Contrary to some fears, the association between TPO antibodies and thyroid cancer remains debatable (Dwivedi et al., 2022). However, their existence does indicate the probability of autoimmune disease, which may evolve into a thyroid disorder over time. According to a study by Prummel, M. & Wiersinga, W. (2005), the presence of these antibodies in euthyroid people (those with normal thyroid function) can predict the risk of developing thyroid dysfunction down the line.
Looking at Thyroid Stimulating Antibodies (TRAb)
In Graves’ disease, thyroid stimulating antibodies (TRAb) mimic the thyroid stimulating hormone (TSH) released by the pituitary gland. This dupes the thyroid into producing excessive hormones despite the pituitary trying to halt its functioning with decreased secretion of TSH.
However, despite successful treatment eliminating the symptoms of the disorder, the presence of TRAb, which arguably triggers Graves’ disease, may remain detectable for many years. This is why, even after seeming recovery, patients might experience a relapse. However, it is important to note that not all patients with detectable TRAb will experience a relapse, as other factors also contribute to this.
The Multiple Layers of Thyroglobulin
Thyroglobulin (Tg) is produced by thyroid cells, both benign and cancerous. It is essentially a protein involved in the production of thyroid hormones. Once a patient has been successfully treated for thyroid cancer, ideally, thyroglobulin should not be detectable in the blood. However, if an increase in thyroglobulin levels occurs, it could act as an early siren for the recurrence of the disease
TPO Antibodies as Radiation Exposure Indicators
In a paper by Albehairy, A., Fathy, S., & Bahriz, R. (2020), they propose that TPO antibodies can serve as predictors for thyroid dysfunction in individuals exposed to radiation. Health professionals working around radiative equipment like those in the radiology departments can consider screening for TPO antibody levels as a precautionary measure.
Even though thyroid antibodies can linger in the body post successful treatment of the disorder, the level of TPOAb does not influence the response to treatment, making repeat measurements generally unneeded. While high TPO antibodies can indeed raise a red flag, they don't directly imply that cancer is on the horizon. They do emphasize that individuals need to keep a vigilant eye on their overall health and routinely consult with healthcare providers.
Remember, you can always improve your thyroid health with Eureka! We offer free personalized recommendations to assist you in enhancing wellness. Be in the know and take control of your health today.
References
- Anti-thyroid peroxidase (anti-TPO) antibodies in thyroid diseases, non-thyroidal illness and controls. Clinical validity of a new commercial method for detection of anti-TPO (thyroid microsomal) autoantibodies by Engler, H., Riesen, W., & Keller, B. (1994). This study evaluates the diagnostic validity of the anti-TPO assay in patients with different types of thyroid disease and controls, establishing a robust method for TPO antibody detection. Read more.
- Anti-thyroid peroxidase antibody in patients with autoimmune thyroid disease: possible identity with anti-microsomal antibody by Portmann, L., Hamada, N., Heinrich, G., & Degroo, L. J. (1985). This paper identifies TPO as the antigen involved in autoimmune thyroid diseases, highlighting its clinical importance. Read more.
- Purification of the human thyroid peroxidase and its identification as the microsomal antigen involved in autoimmune thyroid diseases by Czarnocka, B., Ruf, J., Ferrand, M., Carayon, P., & Lissitzky, S. (1985). This study demonstrates that TPO is the microsomal antigen linked to autoimmune thyroid diseases, confirming its critical role in autoimmunity. Read more.
- Thyroid Autoantibodies. Dwivedi SN, Kalaria T, Buch H (2023). This paper provides recent best practice guidelines in the management of auto-immune thyroid disorders. Read more.
- Thyroid peroxidase autoantibodies in euthyroid subjects by Prummel, M. & Wiersinga, W. (2005). This article discusses the presence of TPO antibodies in euthyroid individuals and their predictive value for developing thyroid dysfunction. Read more.
Thyroid Peroxidase Antibody (TPO) As a Predictor Of Radiation Induced Thyroid Dysfunction Among Nurses And Technicians Working In Mansoura Specialized Medical Hospital: Cross Sectional Study by Albehairy, A., Fathy, S., & Bahriz, R. (2020). This paper evaluates the role of TPO antibodies as a predictor for thyroid dysfunction in individuals exposed to radiation. Read more.
