Thyroid Antibodies
Thyroid antibody tests help determine if an autoimmune disease is the underlying cause of thyroid conditions like hypothyroidism or hyperthyroidism.
What is a thyroid antibody test?
A thyroid antibody test measures the level of thyroid antibodies in your blood. Antibodies are proteins produced by the immune system to fight foreign substances, but in autoimmune disease, they mistakenly attack healthy cells. When these antibodies attack the thyroid, they can cause:
- Hashimoto's disease: The most common cause of hypothyroidism (underactive thyroid), where the thyroid does not produce enough hormones.
- Graves' disease: The most common cause of hyperthyroidism (overactive thyroid), where the thyroid produces too many hormones.
What is it used for?
If thyroid hormone tests indicate your thyroid is not functioning properly, your provider may order antibody tests to identify the cause. Common antibodies tested include:
- Thyroid peroxidase antibodies (TPOAb): High levels suggest Hashimoto's disease.
- Thyroglobulin antibodies (TgAb): High levels suggest Hashimoto's disease.
- Thyrotropin receptor antibodies (TRAb): These can be a sign of Graves' disease.
Why do I need a thyroid antibody test?
You may need this test if you exhibit symptoms of thyroid dysfunction. Symptoms of Hashimoto's disease include weight gain, fatigue, hair loss, cold intolerance, irregular periods, constipation, depression, and joint pain. Symptoms of Graves' disease include weight loss, bulging eyes, hand tremors, heat intolerance, sleep trouble, anxiety, increased heart rate, and goiter.
What happens during the test?
A health care professional will take a blood sample from a vein in your arm using a small needle. The process takes less than five minutes.
Will I need to do anything to prepare?
There are no special preparations necessary for a thyroid antibody blood test.
What do the results mean?
- Negative: No thyroid antibodies were found; symptoms are likely not caused by an autoimmune disease.
- Positive (TPOAb and/or TgAb): May indicate Hashimoto's disease.
- Positive (TPOAb and/or TRAb): May indicate Graves' disease.
The presence of higher levels of antibodies increases the likelihood of an autoimmune thyroid disorder. If diagnosed, medications are available to manage these conditions.
Is there anything else I need to know?
Thyroid disease can worsen during pregnancy and potentially harm the baby. If you have a history of thyroid disease and are pregnant, your provider may monitor your thyroid antibodies and hormone levels, as treatments for thyroid disease are safe during pregnancy.