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)
This test measures the level of thyroid antibodies in your blood to help find out if an autoimmune disease is causing your thyroid to be underactive (hypothyroidism) or overactive (hyperthyroidism). Antibodies are proteins your immune system makes to fight foreign substances, but sometimes they mistakenly attack your own thyroid cells. High levels of certain antibodies can indicate Hashimoto's disease or Graves' 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
No special preparations are needed.
A health care professional will take a blood sample from a vein in your arm using a small needle. The procedure 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
Your results will be interpreted by your healthcare provider. The following patterns are based on the types of antibodies found.
- Negative (no thyroid antibodies found): Your thyroid symptoms are probably not caused by an autoimmune disease. Limitation: A negative result does not completely rule out all autoimmune thyroid conditions; clinical correlation is needed. Next step: Routine
- Positive for TPOAb and/or TgAb: This may mean you have Hashimoto's disease (the most common cause of hypothyroidism). Limitation: A positive result does not confirm the diagnosis by itself; your provider will consider your symptoms, hormone levels, and other findings. Next step: Prompt
- Positive for TPOAb and/or TRAb: This may mean you have Graves' disease (the most common cause of hyperthyroidism). Limitation: A positive result does not confirm the diagnosis by itself; your provider will consider your symptoms, hormone levels, and other findings. Next step: Prompt
- 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. Discuss all results and follow-up plans with your healthcare provider.
- 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?