All you need to know about thyroid antibodies

A thyroid function result is challenging enough to interpret. Throw antibodies into the mix, and there’s a lot to get your head around. But what value do they add to your blood test results? And what does it mean if your thyroid function is normal but your antibodies are mysteriously raised? 

If you’re new to thyroid blood tests, you can brush up on the basics with our Thyroid Guide. Otherwise, read on to learn more.  

In this article, we cover:  

• What are thyroid antibodies? 
• Are thyroid antibodies part of routine thyroid testing? 
• What are the different types of thyroid antibodies? 
• Is it possible to have autoimmune thyroid disease with normal thyroid antibodies?  
• My antibodies are raised but my thyroid function is normal — what’s going on? 
• How to reduce thyroid antibodies 
• Summary 

What are thyroid antibodies?
 

Before we look at the different types of thyroid antibodies, let’s first understand what an antibody is.  

Antibodies are a type of protein that your body produces to help you get rid of unwelcome visitors, like bacteria, viruses, and other foreign substances. They do this by signalling your immune system to attack and destroy any foreign particles that could be harmful. 

This system isn’t foolproof though. In some people, their immune system is hypersensitive — they end up producing antibodies that attack healthy parts of the body, like the thyroid. This is known as an autoimmune disease. 
 

Are thyroid antibodies part of routine thyroid testing?
 

A routine thyroid check usually includes TSH +/- T4. But if an individual has abnormal thyroid function, an enlarged thyroid, or symptoms of thyroid disease, then thyroid antibodies may be checked too.  

You can check your thyroid antibodies at home with our Advanced Thyroid Function Test or Thyroid Function with Antibodies Blood Test. 
 

What are the different types of thyroid antibodies?
 

Antibodies that attack the thyroid are known as thyroid antibodies.  

The three main types of thyroid antibodies are:  

• Anti-thyroid peroxidase antibodies (TPOAb) 
• Anti-thyroglobulin antibodies (TgAb) 
• TSH receptor antibodies (TRAb) 

These markers can help determine whether thyroid disease is due to an autoimmune disease or not — usually Hashimoto’s or Graves’ disease. Hashimoto’s and Graves’ disease are the most common causes of an underactive and overactive thyroid, respectively. 

Thyroid antibodies are not completely specific to the thyroid gland. There is a degree of cross-reactivity which means other autoimmune conditions may also cause these antibodies to increase. 
 

Anti-thyroid peroxidase or anti-TPO (TPOAb)
 

Anti-TPO antibodies attack thyroid peroxidase, an enzyme in the thyroid that produces thyroid hormones.  

Most people have very small amounts of anti-TPO antibodies detectable in the blood. But when levels rise above 35 IU/ml, the likelihood of an autoimmune thyroid condition increases — a higher anti-TPO titre is associated with a higher TSH level [1].  

Anti-TPO antibodies are raised in [2]:  

• 90% of people with Hashimoto’s disease (usually very high levels) — This is the most common reason for raised antibodies. Levels often decrease over time but rarely normalise completely, even after thyroxine has restored thyroid function to normal. 
• 70% of people with Graves’ disease 
• 10% of people with normal thyroid function — If your thyroid function is normal but your anti-TPO antibodies are raised, you’re more likely to develop an autoimmune thyroid disease in the future [1]. If you already have an autoimmune condition like rheumatoid arthritis, type 1 diabetes, and coeliac disease, you’re more likely to have raised anti-TPO antibodies. 

Low levels of anti-TPO may also be found in pregnancy, in people with thyroid cancer [3] and temporarily with post-viral thyroiditis [4].  
 

Anti-thyroglobulin (TgAb)
 

Thyroglobulin is a protein made by the thyroid gland. It’s used to produce important thyroid hormones, T3 and T4. Sometimes, the body produces antibodies against this protein, known as anti-thyroglobulin antibodies (TgAb). 

Anti-thyroglobulin is raised in [5–7]:  

• 60–85% of people with Hashimoto’s disease 
• 30–60% of people with Graves’ disease 
• 25% of people with thyroid cancer 
• 10% of people with normal thyroid function, especially women over 50 

With Hashimoto’s disease, a higher TgAb is associated with a greater symptom burden. Raised TgAb is associated with fragile hair, facial swelling, oedema of the eyes, and a harsh voice [8]. 

Just like anti-TPO, TgAb may be present with other autoimmune conditions like type 1 diabetes or lupus.  
 

TSH receptor antibodies (TRAb)
 

Some antibodies attack the thyroid-stimulating hormone (TSH) receptor. These are known as TSH receptor antibodies (TRAb). The presence of TRAb usually indicates Graves’ disease. It’s specific enough to make it a gold-standard diagnostic test for this disease, but usually it’s not necessary.  

 TRAb is positive in [5,9]:  

• 90–95% of people with Graves’ disease 
• 10% of people with Hashimoto’s disease 

TRAb levels are often reflective of disease severity. For example, a person with a very high TRAb level is less likely to achieve long-term remission following treatment with anti-thyroid drugs.  

TRAb isn’t necessary to diagnose Graves’ disease but it may be particularly useful in the following situations:  

• For pregnant women with a past or present history of Graves’ disease 
• To investigate an overactive thyroid where the cause is not clear 
• To investigate people with suspected Graves’ with normal thyroid function 
   

What is a normal thyroid antibody level?

The normal range for thyroid antibodies will vary between different laboratories. The ranges below are given as a guide. 

	Normal range
Anti-thyroid peroxidase antibodies (TPOAb)	<34 IU/mL
Anti-thyroglobulin (TgAb)	<115 IU/mL
TSH receptor antibodies (TRAb)	<1.51 IU/L

 

Is it possible to have autoimmune thyroid disease with normal thyroid antibodies?
 

The short answer is yes. Just because your thyroid antibodies are undetectable, this doesn’t rule out Hashimoto’s or Graves’ disease. It’s estimated that 5% of patients diagnosed with Hashimoto’s on ultrasound have no measurable thyroid antibodies. These individuals tend to have a milder form of the disease [10].  

Along the same line, having undetectable levels of TRAb makes Graves’ disease unlikely, but still possible. Around 5% are positive for anti-TPO but negative for TRAb [5]. Sometimes, antibody levels are just too low to detect in the early stages of the disease. 
 

My antibodies are raised but my thyroid function is normal — what’s going on?
 

Some people have raised thyroid antibodies despite normal thyroid function. Data from our customers shows that this pattern occurs in around one in 12 people (8.2%) with no known thyroid disease, in keeping with other studies [2]. 

This scenario is more common in women and tends to increase with age. Our data shows this pattern affects more than one in five people with a known thyroid condition.

If you're not known to have a thyroid condition but have raised thyroid antibodies, there are three likely outcomes: 

• Your antibody levels may gradually normalise with time or at least cause no health problems
• You may go on to develop thyroid disease in the future — your risk is higher with raised antibodies compared to someone with normal antibody levels [1]
• You may be prone to or have an underlying autoimmune condition, such as type 1 diabetes, lupus, rheumatoid arthritis, or coeliac disease — that's because thyroid antibodies aren't completely specific to the thyroid

Because autoimmune conditions are largely influenced by genetics, there's not much you can do to significantly reduce your risk of developing one of these conditions in the future. However, if you have a thyroid condition, there may be ways you can reduce your antibody levels. 
 

How to reduce thyroid antibodies
 

You might be wondering: will my antibodies ever go away? 

If you have Hashimoto’s disease, anti-TPO antibodies rarely go back to normal, but they are likely to decline with effective treatment. Similarly, with Graves’ disease, TRAb levels are likely to improve and may even normalise with surgery and/or anti-thyroid drugs. However, TRAb may return to stopping these drugs.   

Some state that certain supplements can reduce antibody levels, like vitamin D and selenium. This seems to be true for people with thyroid conditions [11,12], but it’s unclear whether this applies to people without thyroid disease. Perhaps the best advice is to lead a healthy lifestyle, eat a varied, thyroid-friendly diet, and maintain a healthy gut microbiome.   
 

Summary of thyroid antibodies and thyroid disease
 

 

_{Figures are estimates based on multiple sources [5–7,9].}  

What can thyroid antibodies tell me about my health? 
 

Thyroid antibodies are an excellent follow-up test if your thyroid function is off-kilter — they can help to determine if your thyroid dysfunction is autoimmune in nature.  

If your antibodies are raised but your thyroid function is normal, it may point to another autoimmune disease or show you’re at increased risk of a thyroid condition.  

If you’d like to check your thyroid health, but you’re not sure which test to go for, head to our Thyroid Blood Test Buying Guide.  

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References 
 

1. Prummel MF, Wiersinga WM. Thyroid peroxidase autoantibodies in euthyroid subjects. Best Pract Res Clin Endocrinol Metab. 2005 Mar;19(1):1–15.
2. Thyroid antibodies explained [Internet]. British Thyroid Foundation. [cited 2022 Oct 24]. Available from: https://www.btf-thyroid.org/thyroid-antibodies-explained
3. Nagayama Y. Thyroid Autoimmunity and Thyroid Cancer - The Pathogenic Connection: A 2018 Update. Horm Metab Res. 2018 Dec;50(12):922–31.
4. Samuels MH. Subacute, Silent, and Postpartum Thyroiditis. Medical Clinics of North America. 2012 Mar 1;96(2):223–33.
5. Ragusa F, Fallahi P, Elia G, Gonnella D, Paparo SR, Giusti C, et al. Hashimotos’ thyroiditis: Epidemiology, pathogenesis, clinic and therapy. Best Pract Res Clin Endocrinol Metab. 2019 Dec;33(6):101367.
6. Thyroglobulin Antibody (THYAB) [Internet]. South Tees Hospitals NHS Foundation Trust. [cited 2022 Oct 25]. Available from: https://www.southtees.nhs.uk/services/pathology/tests/thyroglobulin-antibody-thyab/
7. Rosario PW, Côrtes MCS, Franco Mourão G. Follow-up of patients with thyroid cancer and antithyroglobulin antibodies: a review for clinicians. Endocr Relat Cancer. 2021 Apr;28(4):R111–9.
8. Barić A, Brčić L, Gračan S, Škrabić V, Brekalo M, Šimunac M, et al. Thyroglobulin Antibodies are Associated with Symptom Burden in Patients with Hashimoto’s Thyroiditis: A Cross-Sectional Study. Immunol Invest. 2019 Feb;48(2):198–209.
9. Fröhlich E, Wahl R. Thyroid Autoimmunity: Role of Anti-thyroid Antibodies in Thyroid and Extra-Thyroidal Diseases. Front Immunol. 2017 May 9;8:521.
10. Rotondi M, de Martinis L, Coperchini F, Pignatti P, Pirali B, Ghilotti S, et al. Serum negative autoimmune thyroiditis displays a milder clinical picture compared with classic Hashimoto’s thyroiditis. Eur J Endocrinol. 2014 Jul;171(1):31–6.
11. Zhao R, Zhang W, Ma C, Zhao Y, Xiong R, Wang H, et al. Immunomodulatory Function of Vitamin D and Its Role in Autoimmune Thyroid Disease. Frontiers in Immunology [Internet]. 2021 [cited 2022 Oct 25];12. Available from: https://www.frontiersin.org/articles/10.3389/fimmu.2021.574967
12. Ventura M, Melo M, Carrilho F. Selenium and Thyroid Disease: From Pathophysiology to Treatment. Int J Endocrinol. 2017;2017:1297658.