Anti-TPO antibodies above or below normal: causes in athletes and what to do

When an asterisk appears next to antibodies to TPO on a form, many people immediately look for how to “lower the antibodies”. In reality what has clinical significance is not so much their quantity as 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 tactics clinical guidelines suggest.

What “above” and “below” normal indicate

For anti-TPO the reference range usually has only an upper limit: a result below it is considered negative. The concept of “below normal” here effectively means the absence of antibodies or a negligible amount of them, which is a normal situation and requires no action.

The limits of positivity differ between laboratories because of different determination methods. Therefore a number that is “borderline” in one laboratory may be clearly positive in another. To assess trends it is better to use one laboratory.

Borderline elevated antibodies, just exceeding the limit, have less clinical significance than high titers. However, a high titer by itself also does not indicate the severity of the disease — it only confirms the presence of an autoimmune process.

The main question after detecting antibodies is what thyroid function is now. The answer is given by TSH and free T4, and it is precisely these that determine the next steps.

The main causes of elevated antibodies

The most common cause is chronic autoimmune Hashimoto's thyroiditis. It develops in people with a genetic predisposition, more often in women, and can proceed for years without symptoms. The second most frequent cause is Graves' disease, in which antibodies to TPO are detected in most patients alongside 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 drugs, in particular interferons, amiodarone, some immunotherapeutic agents;
• 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 algae, or iodine-containing preparations can provoke or aggravate thyroiditis in predisposed people. It is useful to check the composition of all supplements being taken.

Training itself, even intense training, does not cause the appearance of antibodies. So a positive test in an athlete most likely reflects an individual predisposition rather than a consequence of load.

Tactics with normal and altered TSH

What to do next depends on the state of gland function. The AACE/ATA guidelines on hypothyroidism suggest distinguishing several clinical scenarios.

With normal function, treatment is not required. A person with antibodies is advised to monitor TSH periodically and to pay attention to symptoms: fatigue, cold intolerance, dry skin, constipation, weight gain or, conversely, palpitations and tremor.

With subclinical hypothyroidism, the decision on therapy is made individually, taking into account the TSH level, symptoms, age, and pregnancy plans. The presence of antibodies increases the likelihood of progression to overt hypothyroidism, so the doctor may consider treatment earlier.

With overt hypothyroidism, levothyroxine is prescribed, the dose of which the endocrinologist selects by 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 for Hashimoto's. A meta-analysis by Toulis and colleagues showed that taking selenium may lower the anti-TPO titer, but the effect on gland function and clinical outcomes remains unconvincing. An excess of selenium is toxic, so exceeding the usual recommended amounts on your own is not advisable.

As for iodine, the strategy is simple: allow neither a deficiency nor an excess. Ordinary nutrition with iodized salt is usually sufficient, and high-dose iodine supplements can be harmful in autoimmune thyroiditis.

Gluten-free diets are often recommended for Hashimoto's, but there is no convincing evidence of benefit for people without celiac disease. Since celiac disease occurs more often in people with autoimmune thyroiditis, screening for it is appropriate when there are corresponding symptoms.

Vitamin D, zinc, “cleanses”, and similar interventions have no proven ability to stop the autoimmune process. Correcting deficiencies makes sense for overall health, but it should not be regarded as treatment for thyroiditis.

Special situations in athletes

For female athletes planning a pregnancy, positive antibodies to TPO are a reason to consult an endocrinologist already at the planning stage. During pregnancy the need for thyroid hormones increases, and monitoring of TSH should be more frequent.

Athletes who use prescription drugs should know that androgens change the level of thyroxine-binding globulin, and therefore total T4 and T3. That is why free hormone fractions and TSH are better used for assessing function.

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 load is made by the doctor.

Self-prescribing thyroid hormones “prophylactically” or for weight loss is unacceptable. It can mask the real state of the gland, cause iatrogenic thyrotoxicosis, and lead to loss of bone mass.

Editorial conclusions

Elevated antibodies to TPO most often indicate autoimmune thyroiditis, which for a long time may not affect thyroid function. A negative result (“below normal”) is a normal situation.

Tactics are 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 gland function on a doctor's recommendation.

To continue the topic, we recommend our materials on what the anti-TPO test shows, on subclinical hypothyroidism in athletes, and on selenium in sports nutrition.

References

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