Thyroid Antibodies (TPO + Thyroglobulin)
Detect autoimmune thyroid conditions like Hashimoto's disease or Graves' disease by measuring antibodies that may be attacking thyroid tissue.
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What this test measures
This test measures two key antibodies that can indicate autoimmune thyroid conditions: thyroid peroxidase antibodies (TPO) and thyroglobulin antibodies (TgAb). These are proteins produced by the immune system that mistakenly target normal thyroid proteins as foreign substances. Thyroid peroxidase (TPO) is an enzyme found in the thyroid gland that plays a critical role in producing thyroid hormones, including T3 and T4, by helping add iodine to thyroglobulin. Thyroglobulin is a protein made by the thyroid gland that is used to produce important thyroid hormones, T3 and T4.
These antibodies often develop in people with autoimmune thyroid diseases, such as Hashimoto's thyroiditis and Graves' disease. The presence of TPO antibodies in the blood can signal an autoimmune cause of thyroid disease. TPOAb and TgAb are polyclonal antibodies of the immunoglobulin G (IgG) class. They have a complement fixing and cytotoxic capacity, but their role in Hashimoto's disease still is not clear and seems to be a response to thyroid injury. When these antibodies are elevated, they may indicate ongoing immune system activity against the thyroid gland, which can lead to inflammation and potentially affect thyroid function over time.
What's included
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals experiencing symptoms that could suggest thyroid problems, such as unexplained fatigue, weight changes, hair loss, mood changes, or temperature sensitivity
- Those with a family history of autoimmune thyroid conditions like Hashimoto's disease or Graves' disease, as these conditions often run in families
- People who have been diagnosed with other autoimmune conditions such as type 1 diabetes, rheumatoid arthritis, or celiac disease, which may increase thyroid antibody risk
- Individuals with abnormal TSH or thyroid hormone test results who need further evaluation to determine if an autoimmune process is involved
- Women who are pregnant or planning pregnancy and have a personal or family history of thyroid disease, as thyroid antibodies can affect pregnancy outcomes
- Those being monitored for thyroid cancer recurrence after treatment, as thyroglobulin antibodies can interfere with tumor marker testing
What to expect
Preparation
No fasting is required for this test. Individuals should inform their healthcare provider about biotin supplements, as high doses may interfere with test results and should typically be stopped 72 hours before testing. No other special preparation is needed.
Sample Type
A simple blood draw from a vein in the arm, similar to routine blood work
Collection
The blood sample collection typically takes just a few minutes. A healthcare professional will clean the area, insert a small needle to draw blood into a collection tube, and apply a bandage afterward.
Turnaround
Results are typically available within 1-3 business days after the laboratory receives the sample
Understanding your results
Thyroid antibody results are typically reported in international units per milliliter (IU/mL), with reference ranges that may vary slightly between laboratories. Generally, TPO antibodies are considered normal when less than 35 IU/mL, while thyroglobulin antibodies are typically normal when less than 20 IU/mL. The absolute concentration is very important in the interpretation of the test, and monitoring antibody titers is important to evaluate disease progression over time, though the same assay should be used for consistent monitoring.
| Population | Reference Range | Notes |
|---|---|---|
| Adults | TPO Antibodies: < 35 IU/mL; Thyroglobulin Antibodies: < 20 IU/mL | Values above these thresholds may indicate autoimmune thyroid activity |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
It is not possible for thyroid antibodies to be too low. Normal or undetectable levels of these antibodies typically indicate that an autoimmune process is not currently affecting the thyroid gland. However, it's worth noting that some individuals with autoimmune thyroid conditions may have antibody levels that are too low to detect, particularly in early stages of disease. Normal antibody levels combined with normal thyroid function tests generally suggest that autoimmune thyroid disease is unlikely, though other causes of thyroid dysfunction should still be considered if symptoms are present.
What does a “High” result mean?
Elevated TPO antibodies may indicate Hashimoto's disease if TSH levels are also high, or may suggest an increased risk of developing hypothyroidism later in life if thyroid function is currently normal. TPO antibodies are present in roughly 90% of people with Hashimoto's thyroiditis and in half to three-quarters of people with Graves' disease. Elevated thyroglobulin antibodies may also indicate Hashimoto's disease. It's important to note that 10-15% of people with no thyroid disorder can have raised TPO antibodies, and high TPO antibodies may increase the risk of developing a thyroid disorder in the future. Having elevated antibodies doesn't necessarily mean immediate thyroid dysfunction, but indicates that the immune system is showing activity against thyroid tissue.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your thyroid antibody test results remain completely confidential and are <u>not reported to your doctor</u> unless you choose to share them. This testing is conducted with the highest privacy standards - your results are <u>not part of your medical records</u> and will <u>not appear on insurance statements</u> or explanations of benefits. The laboratory follows strict confidentiality protocols, ensuring that your health information is protected and not shared with employers, insurance companies, or other third parties without your explicit consent. You maintain full control over who has access to your test results, allowing you to make informed health decisions in a private, judgment-free environment. Many individuals appreciate the discretion this testing provides when exploring potential autoimmune thyroid conditions or monitoring their thyroid health without involving their regular healthcare system. No doctor visit is required to order this test, giving you the freedom to take charge of your health screening on your own terms.
Frequently asked questions
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CPT Code: 86376, 86800
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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