TPO Antibodies Above or Below Normal: Causes in Athletes and What to Do
When a little asterisk appears next to TPO antibodies on a lab form, many people immediately look for how to “lower the antibodies.” In reality, the clinical significance lies not so much in their quantity as in the state of thyroid function. The editorial team examines why antibodies can be elevated, what “below normal” means, which situations are typical for athletes and what approach clinical guidelines suggest.
What “above” and “below” normal actually indicate
For anti-TPO the reference range usually has only an upper limit: a result below it is considered negative. The notion of “below normal” here effectively means the absence of antibodies or their negligible amount, which is a normal situation and requires no action.
The thresholds of positivity differ between laboratories because of different assay methods. So a figure that is “borderline” in one laboratory may be clearly positive in another. To assess a trend it is better to use a single laboratory.
Borderline elevated antibodies that barely exceed the threshold have less clinical significance than high titers. However, even a high titer by itself does not indicate the severity of the disease — it only confirms the presence of an autoimmune process.
The main question after antibodies are detected is what the thyroid function is right now. The answer is given by TSH and free T4, and the further steps depend precisely on them.
The main causes of elevated antibodies
The most frequent cause is chronic autoimmune Hashimoto’s thyroiditis. It develops in people with a genetic predisposition, more often in women, and can run without symptoms for years. The second most frequent cause is Graves’ disease, in which TPO antibodies are found in most patients along with antibodies to the TSH receptor.
- hereditary predisposition and autoimmune diseases in the family;
- female sex and age;
- the postpartum period (postpartum thyroiditis);
- excessive iodine intake in predisposed people;
- certain medications, in particular interferons, amiodarone, some immunotherapeutic drugs;
- other autoimmune diseases: type 1 diabetes, celiac disease, vitiligo.
For athletes, excess iodine is of practical interest. High doses of iodine from kelp-based supplements, “fat burners” with seaweed or iodine-containing preparations can provoke or worsen thyroiditis in predisposed people. It is useful to check the composition of all supplements being taken.
Training by itself, even intense training, does not cause antibodies to appear. So a positive test in an athlete most likely reflects an individual predisposition rather than a consequence of loads.
Approach with normal and altered TSH
What to do next depends on the state of thyroid function. The AACE/ATA guidelines on hypothyroidism suggest distinguishing several clinical scenarios.
| Scenario | What it means | Typical approach (determined by the doctor) |
|---|---|---|
| Anti-TPO +, TSH and free T4 normal | An autoimmune process without functional impairment | Observation, periodic monitoring of TSH |
| Anti-TPO +, TSH moderately elevated, T4 normal | Subclinical hypothyroidism | Repeat testing, an individual decision on treatment |
| Anti-TPO +, TSH high, T4 reduced | Overt hypothyroidism | Replacement therapy with levothyroxine |
| Anti-TPO +, TSH suppressed, T4/T3 elevated | Thyrotoxicosis | Further work-up: TSH receptor antibodies, ultrasound, scintigraphy |
With normal function no treatment is needed. A person with antibodies is advised to monitor TSH periodically and also to pay attention to symptoms: fatigue, feeling cold, dry skin, constipation, weight gain or, conversely, palpitations and tremor.
In subclinical hypothyroidism the decision on therapy is made individually taking into account the TSH level, symptoms, age and pregnancy plans. The presence of antibodies raises the likelihood of progression to overt hypothyroidism, so a doctor may consider treatment earlier.
In overt hypothyroidism levothyroxine is prescribed, with the dose selected by an endocrinologist according to body weight, age and TSH level. After stabilization the athlete can train fully.
Selenium, iodine, diets: what science says
Selenium is the most popular supplement in Hashimoto’s. A meta-analysis by Toulis and colleagues showed that taking selenium can lower the titer of TPO antibodies, but the effect on thyroid function and clinical outcomes remains unconvincing. Excess selenium is toxic, so exceeding the usual recommended amounts on your own is not advisable.
As for iodine, the strategy is simple: neither deficiency nor excess should be allowed. Ordinary nutrition with iodized salt is usually enough, while high-dose iodine supplements in autoimmune thyroiditis can be harmful.
Gluten-free diets are often recommended in Hashimoto’s, yet there is no convincing evidence of benefit for people without celiac disease. Since celiac disease is more common in people with autoimmune thyroiditis, with the appropriate symptoms it is reasonable to be screened for it.
Vitamin D, zinc, “detox” and similar interventions have no proven ability to stop the autoimmune process. Correcting deficiencies makes sense for general health, but it should not be seen as a treatment for thyroiditis.
Special situations in athletes
For female athletes planning pregnancy, positive TPO antibodies are a reason to consult an endocrinologist already at the planning stage. During pregnancy the need for thyroid hormones increases, and TSH monitoring should be more frequent.
Athletes who use prescription drugs should know that androgens change the level of thyroxine-binding globulin, and hence total T4 and T3. Therefore, to assess function it is better to use the free fractions of the hormones and TSH.
If thyrotoxicosis develops against the background of positive antibodies, intense training before the condition stabilizes can be dangerous because of tachycardia and the risk of rhythm disturbances. The decision to return to loads is made by the doctor.
Self-prescribing thyroid hormones “preventively” or for weight loss is unacceptable. It can mask the real state of the gland, cause iatrogenic thyrotoxicosis and loss of bone mass.
Editorial conclusions
Elevated TPO antibodies most often indicate autoimmune thyroiditis, which for a long time may not affect thyroid function. A negative result (“below normal”) is a normal situation.
The approach is determined not by the antibody titer but by the level of TSH and free T4. Athletes should avoid excess iodine, not rely on unverified “antibody-lowering schemes” and regularly monitor thyroid function on a doctor’s recommendation.
To continue the topic we recommend our materials on what a TPO antibody test shows, on subclinical hypothyroidism in athletes and on selenium in sports nutrition.
References
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- Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association task force on thyroid hormone replacement. Thyroid. 2014;24(12):1670–1751.
- Hollowell JG, Staehling NW, Flanders WD, et al. Serum TSH, T4, and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab. 2002;87(2):489–499.
- Vanderpump MP, Tunbridge WM, French JM, et al. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey. Clin Endocrinol (Oxf). 1995;43(1):55–68.
- Caturegli P, De Remigis A, Rose NR. Hashimoto thyroiditis: clinical and diagnostic criteria. Autoimmun Rev. 2014;13(4–5):391–397.
- Alexander EK, Pearce EN, Brent GA, et al. 2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid. 2017;27(3):315–389.
- Toulis KA, Anastasilakis AD, Tzellos TG, Goulis DG, Kouvelas D. Selenium supplementation in the treatment of Hashimoto's thyroiditis: a systematic review and a meta-analysis. Thyroid. 2010;20(10):1163–1173.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
