TPO Antibodies: Normal Levels, Test, and Meaning

What Is TPO Antibodies?

TPO antibodies are proteins made by the immune system. They target an enzyme in the thyroid gland called thyroid peroxidase (TPO). This enzyme helps produce thyroid hormones, which control energy use, metabolism, and many body functions.

When the immune system creates these antibodies, it can attack thyroid tissue. This may cause the gland to work less effectively. Doctors use TPO antibody levels to check for autoimmune thyroid diseases such as Hashimoto’s disease or Graves’ disease. Testing helps confirm the cause of thyroid problems when hormone levels are not normal.

When Is TPO Antibodies Testing Recommended?

Doctors may order this test if they suspect thyroid disease. It is often used when other thyroid test results look unusual.

You may need the test if:

• You have symptoms of thyroid disease - such as fatigue, weight changes, or swelling in the neck.
• Other thyroid hormone tests are abnormal - like TSH or T4 results.
• You are pregnant or planning pregnancy - high levels may increase the risk of thyroid problems after birth.
• You have another autoimmune disease - such as type 1 diabetes or rheumatoid arthritis, which raise the risk of thyroid issues.
• A family history of thyroid disease is present - doctors may check for early signs of problems.

How Is TPO Antibodies Testing Conducted?

The test is done with a simple blood draw. A small sample of blood is taken from your arm and sent to a lab for analysis.

TPO antibody testing is often part of a thyroid panel, which may also include TSH, T3, and T4 measurements. These combined results give a clearer picture of thyroid health.

Special preparations are usually not needed. Still, your doctor may ask about supplements like biotin, which can interfere with thyroid test accuracy. Always tell your healthcare provider about any vitamins or supplements you take.

What Are the Normal TPO Antibodies Levels?

Normal levels of TPO antibodies are usually less than 30 IU/mL. Values above this range may suggest an autoimmune reaction.

Note: The units of measurement and the normal ranges can differ depending on the laboratory and the specific methods used.

What Do Abnormal Levels Mean?

TPO Antibodies High Levels

High TPO antibody levels show that the immune system is attacking the thyroid. This does not always mean you have thyroid disease, but the risk is higher.

Possible causes include:

• Hashimoto’s disease - the immune system damages the thyroid, often leading to low hormone production.
• Graves’ disease - the antibodies may contribute to an overactive thyroid.
• Other autoimmune diseases - such as type 1 diabetes or lupus, which may increase antibodies even without thyroid symptoms.
• Pregnancy-related thyroid issues - antibodies may rise during or after pregnancy, increasing the chance of thyroid problems.

Some people worry that high TPO antibodies may mean cancer. Find out if high TPO antibody levels mean cancer.

• Have regular thyroid function tests to monitor changes.
• Share your symptoms with your doctor, even if mild.
• Support thyroid health with balanced nutrition and stress management.
• Follow up as advised if planning pregnancy or already pregnant.

TPO Antibodies Low Levels

Low or absent TPO antibodies are usually normal. They show no autoimmune attack on the thyroid. However, in rare cases, a person may still have thyroid disease without detectable antibodies.

Possible causes of low or absent antibodies:

• Healthy thyroid function - most people with normal thyroid health show no antibodies.
• Non-autoimmune thyroid disease - thyroid issues from other causes, such as iodine imbalance.
• Laboratory variation - different tests may show slightly different results.

• Continue routine thyroid checks if symptoms are present.
• Discuss results with your doctor to rule out other thyroid conditions.
• Keep a healthy lifestyle to support overall thyroid health.

Which Specialist Should You Consult?

If your test shows abnormal results, you should consult an endocrinologist. This doctor specializes in hormone and thyroid conditions. A primary care doctor may also guide you and refer you to a specialist if needed.