Thyroid stimulating antibodies, also called thyroid stimulating immunoglobulin (TSI), are IgG antibodies that bind the TSH receptor and switch it on. This makes the thyroid overproduce hormone, which is the cause of Graves’ disease.
What a positive result means: TSI is a specific type of TSH receptor antibody (TRAb). A positive result, especially with a low TSH, likely points to Graves’ disease. About 95% of people with Graves’ have raised TRAb, according to Cleveland Clinic and the British Thyroid Foundation.
Reference range: TSI is generally considered normal below 0.55 IU/mL, but ranges vary by lab, so always compare against the range printed on your own report. You can see how the test is offered in practice in the Mayo Clinic Laboratories test catalog.
Not always conclusive: A person can occasionally test negative and still have Graves’ disease. In that case, a thyroid scan can confirm the diagnosis.
Eye involvement: In a study of 86 patients, the ratio of thyroid-stimulating antibody to TRAb identified active Graves’ orbitopathy (thyroid eye disease) with 91% sensitivity and 95% specificity at a cutoff of 87.
Pregnancy: These antibodies can cross the placenta, so they matter for pregnant women with a history of Graves’ disease.
Antibody results should always be read alongside TSH and T4 levels and your symptoms. Ask your healthcare provider to explain your results.
At glance:
Thyroid antibodies at a glance
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Thyroid antibodies are immune proteins that show up in your blood when the immune system attacks the thyroid. The main ones are thyroid peroxidase antibodies (TPOAb), thyroglobulin antibody (TgAb), thyroid stimulating immunoglobulin (TSI) and TSH receptor antibodies (TRAb). This guide explains each thyroid antibody test name, the thyroid antibodies normal range, how to read your thyroid antibody test results, and which thyroid antibodies symptoms to watch for. Thyroid stimulating antibodies bind the TSH receptor and switch it on, so the thyroid makes too much hormone. That is the cause of Graves’ disease.
~95%of people with Graves’ disease have raised TRAb
< 0.55 IU/mLtypical TSI reference value (varies by lab)
~50%of Graves’ patients show some sign of eye disease
Antibodies are protective proteins made by your immune system. They normally attack bacteria and viruses. Sometimes the immune system makes autoantibodies that attack healthy tissue instead. Most people carry small amounts of autoantibodies, but large amounts can signal an autoimmune condition.
High thyroid antibodies appear when the immune system has targeted thyroid cells. They develop when the immune system mistakenly attacks thyroid tissue, which can lead to inflammation, tissue damage or disrupted thyroid function. This is what drives autoimmune thyroid disorders such as Graves’ disease and Hashimoto’s thyroiditis.
Antibody
Main association
Thyroid peroxidase antibodies (TPOAb)
Hashimoto’s thyroiditis; sometimes raised in Graves’ disease
Thyroglobulin antibodies (TgAb)
Hashimoto’s; also used to monitor thyroid cancer follow-up
TSH receptor antibodies (TRAb)
Graves’ disease (can be stimulating or blocking)
Thyroid stimulating immunoglobulin (TSI)
A specific stimulating type of TRAb; the main antibody signalling Graves’ disease
There is no single “thyroid antibody test.” Your provider may order one or more tests, and each antibody can go by several similar-sounding names, so ask if you are unsure what appears on your report.
Thyroid antibody test name
Also called
What it helps find
Thyroid peroxidase antibodies
TPOAb, anti-microsomal antibodies
Hashimoto’s disease (main antibody)
Thyroglobulin antibody
TgAb
Hashimoto’s; follow-up after thyroid cancer treatment
Thyroid stimulating immunoglobulin
TSI
Graves’ disease (main antibody)
TSH receptor antibodies
TRAb, TSHR Ab
Graves’ disease
Laboratories list these under their own catalogue names. For example, one reference laboratory lists the stimulating antibody test as Thyroid Stimulating Immunoglobulin, Serum. Antibody tests usually follow abnormal TSH or T4 results, so it helps to understand thyroid function tests (TFTs) first.
Thyroid peroxidase (TPO) is an enzyme in thyroid cells that helps the thyroid use iodine to build thyroid hormone. In autoimmune thyroid disorders, TPO is one of the main targets of the immune system, which is why thyroid peroxidase antibodies are the main antibody signalling Hashimoto’s disease.
Positive TPOAb with high TSH: may mean Hashimoto’s disease.
Positive TPOAb with normal or near-normal TSH: you may develop hypothyroidism later in life. About 50% of people with positive TPOAb and borderline thyroid disease progress to overt hypothyroidism over around 20 years.
Negative TPOAb with high TSH: something else may be causing the underactive thyroid, such as a viral infection or a medicine.
How common: TPOAb are found in more than 90% of people with autoimmune hypothyroidism, and in about 10% of people without a thyroid disorder.
Repeat testing: It is normally only necessary to measure TPOAb once, because the level does not usually change the treatment given.
Thyroglobulin is a protein made by thyroid cells that helps the body create, store and release thyroid hormones. A thyroglobulin antibody test checks whether your immune system is attacking that protein.
Hashimoto’s disease: A positive TgAb may mean Hashimoto’s disease, but TgAb are also found in about 10% of the general population.
Limited extra value: For people with a raised TSH, thyroglobulin antibodies generally add nothing to the TPO antibody result.
Thyroid cancer follow-up: After surgery and radioactive iodine treatment, thyroglobulin should not be detectable. Rising TgAb may mean the cancer has come back, and TgAb can also affect how accurately thyroglobulin is measured, so providers monitor it regularly.
Typical normal range: less than 4 IU/mL (check your own lab’s range).
It is a specific type of TRAb, so a positive TSI test likely means Graves’ disease.
It was originally called long-acting thyroid stimulator (LATS), because its effect lasted much longer than that of TSH, before it was recognised as an immunoglobulin.
These are functional antibodies, not just markers. They actively drive the disease rather than merely indicating it.
TRAb are often present before clinically detectable hyperthyroidism develops.
Normally the pituitary gland releases TSH, which tells the thyroid to make hormone. When thyroid hormone is high, the pituitary lowers TSH. In Graves’ disease, TSI mimics TSH, so the thyroid keeps working even when the pituitary tries to switch it off.
Simplified diagram of TSH signalling versus TSI signalling.
The same mechanism is described in the reference literature: in Graves’ disease, hyperactivity of the thyroid is due to a thyroid-stimulating antibody that binds the TSH receptor and, in doing so, activates it, producing thyroid hormone independently of TSH.
TSH receptor antibodies are not all the same. The group can either stimulate the receptor or block it.
Stimulating (TSI)
Activate the TSH receptor and cause Graves’ hyperthyroidism.
Blocking (TBII)
Less commonly, block the receptor from binding TSH, which can cause hypothyroidism.
Both types can occur at the same time. Both can also cross the placenta in pregnancy and affect the baby’s thyroid function.
Because TRAb is a broad term covering both kinds, the British Thyroid Foundation describes TRAb as potentially stimulatory and blocking, while TSI is the stimulatory antibody specific to Graves’ disease.
Doctors usually start with a standard thyroid panel. If TSH and T4 are abnormal and an autoimmune cause is suspected, one or more antibody tests may be ordered. If you are unfamiliar with the first-line blood work, see our guide to thyroid function tests (TFTs).
Common reasons for an antibody test include:
Abnormal TSH or T4 results, to find the cause of high or low thyroid hormone levels.
Suspected Graves’ disease or Hashimoto’s disease.
Monitoring thyroid conditions during pregnancy.
Checking for thyroid cancer recurrence (this uses thyroglobulin antibodies rather than TSI).
Worth knowing: One reference text advises that, without evidence of thyroid dysfunction, thyroid antibodies should not be measured except in special circumstances, such as a history of recurrent miscarriages.
No special preparation is usually needed. You can eat and drink normally unless your provider says otherwise.
It is a simple blood draw. A phlebotomist takes blood from a vein in your arm, and the test can be done at a laboratory at any time of day.
Tell your provider about biotin. Supplements containing biotin can cause inaccurate results. Ask how long to stop them beforehand. The Immunoassay Handbook also notes that assays using streptavidin can be affected by biotin therapy.
If you take supplements for thyroid health, read our overview of hypothyroid supplements and check the label for biotin before your blood test.
Results are usually reported as negative or positive. A negative result means the antibody level is within the normal range. A positive result means it is higher than the normal range. Typical reference values are:
Test
Typical normal range
Thyroid peroxidase antibody (TPOAb)
Less than 5.6 IU/mL
Thyroglobulin antibody (TgAb)
Less than 4 IU/mL
Thyroid stimulating immunoglobulin (TSI)
Less than 0.55 IU/mL
TSH receptor antibody (TRAb)
Less than 1.75 IU/L or less than 3.3 IU/L, depending on the type of test
Compare with your own lab’s range. Labs can use different reference ranges, so do not compare your value with a range from another laboratory. Your report shows the range that applies to you. Another reference text lists the TRAb reference interval simply as absence of detectable antibody.
Thyroid antibody test results: positive and negative
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Thyroid antibody test result
What it may mean
Positive TPOAb with high TSH
May mean Hashimoto’s disease
Positive TPOAb with normal TSH
May develop hypothyroidism later
Negative TPOAb with high TSH
Another cause of underactive thyroid is likely
Positive TgAb
May mean Hashimoto’s disease
Positive TRAb with low TSH
Likely Graves’ disease
Positive TSI
Likely Graves’ disease
Positive TRAb with low TSH likely means Graves’ disease. About 95% of people with Graves’ disease have raised TRAb, and about 70% also have raised TPOAb.
Positive TSI likely means Graves’ disease.
A positive result is not always disease. Some people test positive for antibodies without having thyroid disease.
A negative result does not always rule it out. In rare cases TRAb is negative yet Graves’ disease is present, and a thyroid scan can confirm the diagnosis.
Sources differ on which test to use. Cleveland Clinic notes that TRAb tests can sometimes give inaccurate results, so TSI is the recommended laboratory test. The British Thyroid Foundation says TSI is not routinely tested and is used mainly as a research tool. A textbook chapter reports that TRAb immunoassays have higher sensitivity than TSI bioassays for separating Graves’ disease from destructive thyroiditis. In practice, which test you get depends on your laboratory and clinician.
Thyroid peroxidase antibodies over 100: what does it mean?
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Many people search for thyroid peroxidase antibodies over 100 after seeing a high number on their report. Here is what the sources support.
It is flagged as positive. Any level above your lab’s reference range is a positive result. One typical TPOAb reference value is less than 5.6 IU/mL, so 100 would be well above it if your report uses the same units.
Units and ranges differ. Labs use different reference ranges, and you should not compare your number with a range from another laboratory.
The number alone does not diagnose disease. What a positive TPOAb means depends on your TSH: with high TSH it may mean Hashimoto’s disease, and with normal TSH it may mean you could develop hypothyroidism later.
The level does not usually change treatment. The British Thyroid Foundation notes that the TPOAb level does not usually influence the treatment given or the response to treatment. Decisions are based on your TSH, T4 and symptoms.
Positives happen without disease. About 10% of people without a thyroid disorder have TPO antibodies.
No cutoff for “dangerous.” The sources provided do not define a TPOAb level that is dangerous or that predicts severity. Ask your provider how your result fits with your TSH and T4, and whether any monitoring is needed.
Thyroid antibodies are detected in a blood test. The thyroid antibodies symptoms people notice come from the thyroid condition they are linked to, and some people with positive antibodies have no thyroid disease at all.
Graves’ disease (overactive thyroid)
Weight loss, fast heartbeat, tremor, bowel discomfort with diarrhoea. Eye symptoms can include irritation, watering, dry gritty eyes and light sensitivity.
Hashimoto’s thyroiditis (underactive thyroid)
Enlarged thyroid (goitre), weight gain, fatigue, depression, hair loss, and constipation.
TRAb levels do more than confirm a diagnosis. They also help guide care.
Severity: The severity of Graves’ disease is often reflected in the TRAb level. When TRAb is very high, long-term remission after a course of antithyroid drugs is less likely.
Stopping medication: Relapse is more likely if antithyroid drugs are stopped while TRAb is still raised. The American Association of Clinical Endocrinologists endorses using TRAb to guide prognosis and therapy, and measuring it helps predict who can come off antithyroid drugs.
Antibodies can linger: After radioactive iodine or surgery, TRAb may stay in the body for many years. After antithyroid drugs they sometimes disappear, but they can return months or years later and cause a relapse.
Repeat testing: Repeating TRAb can inform treatment in Graves’ disease, whereas repeating TPOAb is rarely useful.
Treatment options for Graves’ disease
Graves’ disease has several treatment options, including pills and procedures. Your care team will explain the next steps after abnormal results. For a broader look at what can and cannot be reversed, see how to cure thyroid problems.
Graves’ orbitopathy (GO) is the most common extrathyroidal manifestation of Graves’ disease. It involves inflammation and remodelling of the tissues around the eye. Around 50% of people with Graves’ disease have some sign of eye disease, and about 5% develop a severe form that can cause bulging of the eyes, corneal exposure and double vision. Symptoms range from irritation, watering and dry, gritty eyes to light sensitivity.
What the research shows
Early immunosuppressive treatment during the active phase of GO can reduce disease activity and severity, so sensitive screening tests are valuable. A study of 86 patients with GO (Nakano and colleagues, Endocrine Practice, 2022) looked at the ratio of thyroid-stimulating antibody to TSH receptor antibody:
81%correct classification of MRI results
92%in patients without T3-predominant Graves’
91% / 95%sensitivity / specificity at a cutoff ratio of 87
The authors concluded the ratio is a highly sensitive and specific indicator of active GO, especially in patients without T3 predominance, and a good screening test in primary care. This is a single study, so it supports the idea rather than settling it.
TSI and TRAb are IgG antibodies, and IgG crosses the placenta. This is why antibody testing matters in pregnancy for women with Graves’ disease.
Stimulating and blocking antibodies can both reach the baby and affect fetal thyroid function and goitre.
Neonatal thyrotoxicosis is most commonly caused by TSI passing from a mother with Graves’ disease. TSI may continue to be produced even years after thyroidectomy or radioiodine treatment, so it is important to identify these women in pregnancy.
When TSI is the cause, the baby’s thyrotoxicosis is transient and limited by clearance of the maternal antibody. It usually settles by about 20 weeks.
Maternal TSI levels in the third trimester and the infant’s levels correlate well with neonatal hyperthyroidism, which occurs in almost all cases when levels exceed five times normal.
Babies of mothers with a history of Graves’ disease are examined and have thyroid blood tests around day 3 and again between days 10 and 14.
Graves’ disease is autoimmune hyperthyroidism driven by stimulating antibodies. Hashimoto’s thyroiditis is autoimmune hypothyroidism, usually marked by TPO antibodies, and TPO antibodies usually remain even after medication normalises thyroid levels. About 50% of people with positive TPOAb and borderline thyroid disease progress to overt hypothyroidism over roughly 20 years. If you have an underactive thyroid, our guides on a hypothyroidism diet plan (PDF) and a thyroid diet chart (PDF) may help, and women in midlife can read about menopause and an underactive thyroid.
Symptoms you may notice
Overactive thyroid in Graves’ disease is linked with weight loss, fast heartbeat, tremor and diarrhoea, while Hashimoto’s symptoms include weight gain, fatigue, depression and hair loss. To explore these in more depth, see thyroid and weight and thyroid disorders and hair loss.
Other autoimmune conditions
Autoimmune thyroid disease raises the chance of another autoimmune condition, such as Addison’s disease, pernicious anaemia or coeliac disease, but the risk is still very small. Doctors consider these if new or unexplained symptoms appear.
Nodules and scans
A thyroid scan can help diagnose Graves’ disease when antibodies are negative, and a nodule found with normal thyroid tests warrants an ultrasound. Learn about options in how to remove thyroid nodules without surgery.
Thyroid stimulating antibodies (TSI, a type of TRAb) bind and activate the TSH receptor, making the thyroid overproduce hormone. This causes Graves’ disease.
A positive TRAb or TSI with a low TSH likely means Graves’ disease, but a negative result does not always rule it out.
Thyroid peroxidase antibodies and thyroglobulin antibody point mainly to Hashimoto’s, while thyroid stimulating immunoglobulin and TRAb point to Graves’ disease.
Always compare your result with the reference range printed on your own lab report, and tell your provider if you take biotin.
TRAb levels can help predict severity and relapse risk, and they matter for eye disease.
In pregnancy, these antibodies cross the placenta and can affect the baby, so testing and monitoring are important.
Medical disclaimer: This article is for general education and does not replace advice from your doctor. Antibody results should be read alongside TSH, T4 and your symptoms. Ask your healthcare provider to explain your results.
Frequently asked questions
What is the thyroid antibody test name?
There are several: thyroid peroxidase antibodies (TPOAb), thyroglobulin antibody (TgAb), thyroid stimulating immunoglobulin (TSI) and TSH receptor antibodies (TRAb). Your provider chooses based on your TSH and T4 results and symptoms.
What are thyroid antibodies symptoms?
Antibodies themselves are found by a blood test. Symptoms come from the related condition: weight loss, fast heartbeat and tremor in Graves’ disease, or fatigue, weight gain and hair loss in Hashimoto’s thyroiditis.
What does thyroid peroxidase antibodies over 100 mean?
It is a positive result if your lab’s range is much lower, but the meaning depends on your TSH and T4. The level alone does not usually change treatment, so ask your provider how to interpret it.
Do thyroid stimulating antibodies ever go away?
Sometimes. They can disappear after a course of antithyroid drugs but may return months or years later. After radioactive iodine or surgery they can remain for many years.
Do I need to fast before a TSI or TRAb test?
Usually no. You can eat and drink normally unless your provider says otherwise, but mention any biotin supplements.
Is a positive antibody always a sign of thyroid disease?
No. Some people test positive without having thyroid disease, which is why results are interpreted with TSH and T4.
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Also known as TSI (Thyroid Stimulating Immunoglobulins), thyroid stimulating antibodies are referred to as proteins in your immune system that erroneously connect to the TSH Receptor Antibodies on your thyroid gland, which thereby forces it to produce more than enough hormones.
TRAb (thyroid-stimulating antibodies) are secreted by an individual's pituitary gland and are capable of imitating thyroid-stimulating hormone (TSH), which causes your thyroid to keep producing thyroid hormones, even when your pituitary attempts to block the thyroid from producing thyroid-stimulating hormones.
The thyroid-stimulating antibodies are associated with Graves’ disease, and the presence of these antibodies suggests that you may have Graves’ disease. In individuals, these antibodies lead to an overactive thyroid gland.
This article will give you more information and an in-depth understanding of what you need to know about thyroid-stimulating antibodies, as well as other related matters.
Thyroid Stimulating Antibodies (What They Are)
Although there are several kinds of antibodies, which are capable of affecting your body in several ways.
Some antibodies affect a particular organ of your body, while others affect many parts of the body.
Thyroid antibodies, to be specific, are autoantibodies that affect your thyroid's ability to produce the needed amount of thyroid hormones, which determines how your body makes use of energy.
This then results into serious autoimmune thyroid diseases like Hashimoto's disease, which is the major cause of hypothyroidism (underactive thyroid).
Hypothyroidism condition is when your thyroid can't produce the required hormones that are needed by the body. This condition makes your body's metabolism to slow down.
Thyroid antibodies also result in serious autoimmune thyroid diseases like Graves' disease, which is the major cause of hyperthyroidism (overactive thyroid).
Hyperthyroidism condition is when your thyroid produces more thyroid hormones than what is needed by your body. This condition causes your body’s metabolism to speed up.
Thyroid Stimulating Antibodies (What They Do)
There are three major activities associated with the thyroid-stimulating antibodies that are secreted by your pituitary gland. Information on this is found below.
â– TRAb (thyroid stimulating antibodies) is the reason for hyperthyroidism. It is this overstimulation that results to overactive thyroid in you as an individual.
â– TRAb (thyroid-stimulating antibodies) always behave like TSH (thyroid-stimulating hormone), which normally signals from the brain.
â– TRAb (thyroid-stimulating antibodies) tend to burden your gland, as they initiate the thyroid to produce large amounts of T3 and T4 hormones.
Is it Possible for Thyroid Antibodies to go away?
Specifically in you as an individual with Graves’ disease, there are medical procedures that help you bring back your thyroid to normal.
These procedures include surgery, antithyroid medication, and radioactive iodine (RAI).
While surgery and radioactive iodine procedures can eliminate thyroid tissue to heal overactivity, the thyroid-stimulating antibodies, which are the root cause of Graves’ disease, could remain in your body for extended periods even after undergoing any of the treatment procedures.
At times, thyroid-stimulating antibodies can disappear after taking antithyroid drugs for a period, but can reappear again months or years after you've stopped antithyroid drugs, which can result in relapse of Graves’ disease.
If you’re an individual with autoimmune hypothyroidism, TPO antibodies often remain in your body, but generally it's possible for thyroid antibodies to leave your body.
If I have Autoimmune Thyroid Disease, am I more likely to develop other Autoimmune Diseases?
While the risk of developing another autoimmune disease is very minimal, it's still likely that it happens.
You as an individual with an autoimmune thyroid disorder, can have Addison’s disease, for instance, which is another autoimmune condition.
Nevertheless, you can only be considered to have such conditions when you have autoimmune thyroid disease and yet develop new or non-specific symptoms.
If I have raised Thyroid Antibodies, but Subclinical Thyroid Disease, am I more likely to develop full-blown Thyroid Disease?
There's definitely a real chance of developing full-blown thyroid disease if you have thyroid antibodies, which may need you to get treatment at some point in time to come.
What is a Thyroid Antibody Test?
Your thyroid is that small gland with a butterfly shape that's found in the lower front of your neck.
It's capable of secreting the hormones that help manage many operations in your body system which include the speed at which you burn calories from the food you eat, as well as your heartbeat.
As a concerned individual, you can undergo this test, which helps you measures the level of thyroid antibodies in a sample of your blood.
This is done to examine if you have an autoimmune thyroid disease.
Will I need to do anything to Prepare for the Test?
To undergo a thyroid antibodies blood test, you practically don't need any particular preparation.
Are there any Risks to the Test?
Generally your symptoms will depart to a great extent, nevertheless you may experience very minimal risks which can include little pain or bruise at the point at which needle was inserted.
What do the Results Mean?
By undergoing thyroid antibody test, probable results may include;
â– Negative
This means that the thyroid symptoms you're experiencing is probably not as a result of autoimmune disease, since there are no thyroid antibodies present.
â– Positive
This result suggests the presence of TRAb, TSI or TPOAb thyroid antibodies, which indicates that you have Hashimoto's disease or Graves ' disease.
Most individuals having these conditions carries high levels of either one or both of these aforementioned antibodies.
So, as much thyroid antibodies that you have determines your likelihood of having a thyroid autoimmune disorder.
Conclusion
As you've had some deeper understanding as regarding thyroid stimulating antibodies, you need to understand that antibodies are generally not harmful.
Infact, they're proteins that help your body's defence system to fight against harmful organisms (like bacteria and viruses) that could make you ill.
However, antibodies can sometimes fight healthy organs and tissues in your body, thinking them to be invaders.
Such antibodies are referred to as autoantibodies, they're produced in your body unwantedly.
Hence, their presence in your blood thereby indicates a sign of autoimmune disease.
