Thyroid Antibodies Test
Reviewed
Also called: Thyroid autoantibodies, Thyroid peroxidase antibody (TPO, anti-TPO), Antithyroid microsomal antibody, Thyroid-stimulating immunoglobulin (TSI), TSH receptor antibody (TRAb), Long-acting thyroid stimulator (LATS)
A thyroid antibody test measures the level of thyroid antibodies in a sample of your blood to check for an autoimmune thyroid disease.
Specimen: Blood sample from a vein in your arm
Why this test may be ordered
- You have symptoms of an underactive or overactive thyroid, such as weight gain or loss, fatigue, hair loss, irregular periods, bulging eyes, tremors, or rapid heart rate.
- Your thyroid hormone tests (T3, T4, TSH) show your thyroid isn't working properly, and your provider wants to see if an autoimmune disease is the cause.
- You have a history of thyroid disease and are pregnant, because thyroid disease can worsen during pregnancy and affect both mother and baby.
Preparation and collection
There are no special preparations necessary for a thyroid antibodies blood test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
The more thyroid antibodies you have, the more likely it is that you have an autoimmune disorder of the thyroid.
- Negative (no thyroid antibodies found): Negative: no thyroid antibodies were found. Limitation: This means your thyroid symptoms are probably not caused by an autoimmune disease. Next step: Your provider will decide which tests to use based on your symptoms, the results of other tests, and information about your medical and family health histories.
- Positive for TPOAb or TgAb: Positive: thyroid antibodies, TPOAb or TgAb, were found. This may mean you have Hashimoto's disease. Limitation: Most people with Hashimoto's disease have high levels of one or both of these types of antibodies. Next step: If you are diagnosed with Hashimoto's disease or Graves' disease, there are medicines you can take to manage your condition.
- Positive for TPOAb, TSI, or TRAb: Positive: thyroid antibodies, TPOAb, TSI, or TRAb, were found. This may mean you have Graves' disease or Hashimoto's disease. Limitation: The more thyroid antibodies you have, the more likely it is that you have an autoimmune disorder of the thyroid. Next step: If you are diagnosed with Hashimoto's disease or Graves' disease, there are medicines you can take to manage your condition.
- The test is not diagnostic on its own; results must be interpreted alongside thyroid hormone levels (T3, T4, TSH), your medical history, family history, and physical exam.
- Some people with autoimmune thyroid disease may have negative antibody tests, and some people without symptoms may have positive antibodies.
- Pregnancy can affect thyroid antibody levels and thyroid function, so results should be interpreted with caution during pregnancy.
What to do next
If you are diagnosed with Hashimoto's disease or Graves' disease, there are medicines you can take to manage your condition.
- What do my specific antibody results mean for my thyroid function?
- Do I need additional tests, such as thyroid hormone levels or imaging?
- How will my results affect my treatment plan?
- If I am pregnant, how do these results affect my pregnancy care?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.