Everything to know about Thyroid Peroxidase Antibodies (TPO)
You have probably heard or come across the term thyroid peroxidase (TPO) antibodies, but may not be quite sure what it means.
Indeed, TPO antibodies are frequently mentioned in terms of thyroid health and diseases that affect it. Proper management of thyroid diseases and keeping the gland healthy require a thorough understanding of thyroid hormones, enzymes, tests, and other aspects that provide insight into the way the butterfly-shaped gland functions.
That’s why in this article we are going to talk about TPO antibodies.
What is thyroid peroxidase?
Before we discuss TPO antibodies, it's useful to give a brief introduction to thyroid peroxidase.
Thyroid peroxidase is defined as a key enzyme in the biosynthesis of thyroid hormones. The enzyme catalyzes iodide oxidation, thyroglobulin iodination, and coupling of iodothyronine.
In other words, TPO, which is found in thyroid follicle cells, converts thyroid hormone to T4 to T3.
Basically, TPO is essential for the proper functioning of the butterfly-shaped gland. Decreased activity or expression of TPO impairs thyroid follicular cell function by decreasing iodide trapping and impairing synthesis of thyroid hormone.
What are thyroid peroxidase antibodies?
An antibody is defined as a protective protein produced by the immune system in response to the presence of a foreign substance called an antigen. Antibodies detect and bind to the antigens with a mission to remove them from the body[i].
In some cases, antibodies attack the body’s own cells, tissues, and organs. This reaction is called autoimmune response. When thyroid antibodies attack healthy cells produced by the butterfly-shaped gland, an autoimmune thyroid disorder can occur.
Thyroid peroxidase functions as a catalyst to the organification and coupling reactions in the production of the T4 hormone. However, thyroid peroxidase antibodies (TPOAbs) prevent it from doing so. The presence of TPO antibodies indicates that the cause of thyroid disease is an autoimmune disorder such as Hashimoto’s thyroiditis and Graves’ disease.
Antibodies that attack thyroid gland induce inflammation and impair the function of this important gland.
Thyroid peroxidase antibodies test and who needs it
Thyroid peroxidase antibodies test measures the level of an antibody that is directed against TPO.
These antibodies are produced in the body by the immune system[ii], as mentioned above.
The TPO antibodies test serves multiple purposes, such as:
- Helping doctors diagnose autoimmune thyroid disorders
- Aiding in differentiating autoimmune thyroid disorders from non-autoimmune hypothyroidism or goiter
- Serves as a diagnostic tool in deciding whether to treat a patient who has been diagnosed with subclinical hypothyroidism
Doctors may also order a TPO antibodies test if you are pregnant and have an autoimmune disease, particularly the condition that involves thyroid.
Thyroid peroxidase antibodies have been associated with reproductive difficulties such as miscarriage, preeclampsia, premature delivery, and in-vitro fertilization failure[iii]. In these instances, the doctor may also order TPOAbs test, but bear in mind it’s not a standard test for problems with fertility and pregnancy.
If a pregnant woman has an autoimmune thyroid condition or some other autoimmune disease with thyroid involvement, the doctor may order TPO antibodies test in order to determine whether the baby could be at risk of thyroid dysfunction.
Additionally, you might need a TPO antibodies test if other thyroid hormone levels are too low or too high. Your doctor will need results from TPO antibodies test to determine whether an autoimmune condition impaired the production and concentration of thyroid hormones.
It’s important to mention that some people with TPO antibodies may not have thyroid disease, but their presence implies there’s a higher risk of developing a condition that affects butterfly-shaped gland.
You may need a TPO antibodies test if you experience symptoms of a thyroid problem that your healthcare provider thinks they may be caused by autoimmune conditions such as Hashimoto’s thyroiditis and Graves’ disease.
Symptoms of Hashimoto’s thyroiditis
At the very beginning, patients may not notice any particular symptom. This autoimmune condition tends to progress slowly over the years and causes thyroid damage and a decline in hormone production.
In fact, Hashimoto's thyroiditis is the most common cause of hypothyroidism, which is why signs and symptoms of this autoimmune disease are similar to the underactive thyroid. Some of them include[iv]:
- Weight gain
- Hair loss
- Puffy face and pale, dry skin
- Increased sensitivity to cold
- Stiff, tender, and aching muscles
- Tongue enlargement
- Brittle nails
- Joint pain
- Depression and impaired memory
Symptoms of Graves’ disease
Similarly to Hashimoto's thyroiditis, Graves' disease may not induce some noticeable symptoms at first as they tend to develop over time in some people.
Graves' disease is the main cause of hyperthyroidism, and some signs and symptoms associated with it include[v]:
- Rapid or irregular heartbeat
- Anxiety and irritability
- Weight loss
- Tremor of hands and fingers
- Bulging eyes
- Heat sensitivity and enhanced perspiration
- Goiter i.e., enlarged thyroid gland
- Menstrual cycle changes
- Frequent bowel movements
- Thick and red skin usually on top of feet or shins
How is the TPO antibodies test performed?
TPO antibodies test is, basically, a blood test. Your healthcare provider or a lab technician will take a sample of your blood in order to measure how many antibodies are in it.
The blood sample is collected by inserting a needle into a vein in the arm. You might feel a little sting when the needle goes in or out. The whole process lasts five minutes maximum. TPO antibodies test requires no special preparations.
However, you should inform the doctor if you're taking some medications, supplements, or herbs. Some drugs and supplements may impair the results.
Based on the information you provide, the doctor will suggest whether you can continue taking the medication or supplement even on the day of the test or not.
Follow the doctor’s recommendations religiously in order to get accurate results and precise diagnosis or insight into your condition.
Are there any risks of TPO antibodies test?
Generally speaking, the TPO antibodies test is safe and is not associated with some severe risks.
However, some patients may experience bleeding, bruising, feeling of lightheadedness, and infection. The likelihood of these minor risks is small, and it doesn't mean that all patients will experience them.
What do the results of TPO antibodies test mean?
The TPO antibodies test results may show one of the following options:
- Negative – as you can already conclude negative TPO antibodies test result indicates that no thyroid antibodies were found. This result also implies that thyroid problems and symptoms a patient experiences are not caused by an autoimmune condition
- Positive antibodies to TPO and/or Tg – this result indicate a patient may have Hashimoto’s thyroiditis
- Positive antibodies to TPO and/or TSH – may indicate the presence of Graves’ disease[vi]
The higher the level of antibodies, the more likely it is that a patient has an autoimmune disease of the thyroid e.g., Hashimoto's or Graves' disease. Blood test results for TPO antibodies are positive in 95% of patients with Hashimoto’s thyroiditis and in 50% to 80% of people with Graves’ disease.
When it comes to TPOAbs, the reference value is <9.0 IU/ml (international units per milliliter). Values above 9.0 are typically associated with autoimmune thyroid disease, but elevations are also observed in some other autoimmune conditions[vii]. The most commonly mentioned TPOAb reference range is less than 35 IU/ml[viii].
The presence of TPOAbs in patients with subclinical hypothyroidism predicts an elevated risk of overt hypothyroidism. Moreover, this also shows that those patients could be at a higher risk of developing other autoimmune conditions like type 1 diabetes.
As mentioned above in the article, some people may be positive to TPO antibodies, but they do not have a thyroid condition.
In cases when thyroid function is normal, and a patient has TPO antibodies, the healthcare provider may suggest periodic checkups in order to prevent or spot thyroid problems in the future[ix].
What do TPO antibodies mean to you?
TPO antibodies test informs the doctor whether symptoms you experience are associated with an autoimmune condition. But, if you already have some thyroid disease, its treatment is not really based on antibody levels.
After all, the treatment of thyroid condition is based on thyroid hormone levels and the severity of symptoms a patient experiences. Doctors order TPO antibodies tests to assess the potential cause of thyroid condition and identify the subclinical disease of the butterfly-shaped gland.
The doctor is less likely to treat the thyroid disease if a patient has high TPO antibodies without symptoms and with normal thyroid hormone levels. On the other hand, if a patient has mild symptoms or borderline abnormal thyroid hormone levels along with higher TPO antibodies, the doctor may recommend treatment. Again, the treatment will work to manage symptoms and normalize levels of thyroid hormones.
How to heal your thyroid
Based on the results of the TPOAbs test, the doctor will recommend certain treatment measures if necessary.
However, there are many things you can do on your own in order to prevent or lower the levels of antibodies. These measures can help delay progression or aid management of autoimmune thyroid conditions. Below, you can see some useful suggestions:
- Modify your diet – the first and most important thing you can do to lower levels of TPO antibodies is to modify your diet. Make sure to lower or avoid intake of heavily processed and refined foods, GMO foods, and foods laden with thickening agents, artificial sweeteners, thickening agents, food dyes, among others. Instead, try to include organic fruits and vegetables into your diet and other foods that are rich in nutrients and with amazing anti-inflammatory activity. You also need to consume fiber-rich foods which are beneficial for the digestive system i.e., your gut. Additionally, your diet also needs protein which assists in the repair of tissues in the body, participates in the transport of thyroid hormones throughout the body
- Manage stress – hectic lifestyle that most of us have nowadays can increase stress levels i.e., elevate cortisol. Like with other hormones, higher cortisol can affect the balance of other hormones and negatively affect our overall health and wellbeing. Thyroid function and stress can be connected. Therefore, to lower TPO antibodies, you should definitely find a unique way to manage stress. There are no rules here, and you should do something you find relaxing e.g., taking deep breaths, counting to ten, yoga, meditation, reading, writing, you name it
- Exercise regularly – physical activity is vital for our health and wellbeing. What most of us don’t realize is that sedentary lifestyle can also be bad news for our immune system function and thereby antibodies, but it also contributes to weight gain, thyroid hormone problems, and whatnot. Make sure you exercise regularly to maintain weight in a healthy range but also to try lowering antibody levels. Find an activity you like doing because that way you are more likely to stick to it and practice it regularly.
Thyroid peroxidase antibodies indicate that the thyroid condition is caused by autoimmune thyroid disease.
In some patients, TPO antibodies are elevated, but without an autoimmune condition, which implies they could be at a higher risk of developing it.
Doctors order TPO antibodies test for various reasons, but the whole process is simple because it's just a blood test which is performed in five minutes maximum.
Some patients may not need treatment for their elevated TPO antibodies, depending on the level of thyroid hormones and the severity of symptoms.
[i] Antibody, biochemistry. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/science/antibody
[ii] Thyroid peroxidase test. MedicineNet. Retrieved from: https://www.medicinenet.com/thyroid_peroxidase_test/article.htm
[iii] Thyroid antibodies. Lab Tests Online. Retrieved from: https://labtestsonline.org/tests/thyroid-antibodies
[iv] Hashimoto's disease. Mayo Clinic. Retrieved from: https://www.mayoclinic.org/diseases-conditions/hashimotos-disease/symptoms-causes/syc-20351855
[v] Graves' disease. Mayo Clinic. Retrieved from: https://www.mayoclinic.org/diseases-conditions/graves-disease/symptoms-causes/syc-20356240
[vi] Thyroid antibodies. Medline Plus. Retrieved from: https://medlineplus.gov/lab-tests/thyroid-antibodies/
[vii] Test ID: TPO. Mayo Clinic Laboratories. Retrieved from: https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/81765
[viii] Antithyroid antibody. Medscape. Retrieved from: https://emedicine.medscape.com/article/2086819-overview
[ix] Thyroid peroxidase antibody test: what is it? Mayo Clinic. Retrieved from: https://www.mayoclinic.org/thyroid-disease/expert-answers/faq-20058114
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