Hyperthyroidism: Prevention, Diagnosis, and When to See a Doctor

Hyperthyroidism is well diagnosed and treated, but only on the condition that it is suspected in time. For an athlete this is also a matter of safety: training against the background of untreated thyrotoxicosis burdens the heart, which is already working in an overload mode. The editorial team explains what can be done to reduce the risk, how the examination proceeds, when emergency care is needed, and how to return to training after treatment.

Prevention: what really works

Graves' disease, the most frequent cause of hyperthyroidism at a young age, has an autoimmune nature and a hereditary predisposition, and there are no reliable ways to prevent it. However, a number of modifiable risk factors are known, and they are worth heeding.

The simplest and most important step for an athlete is not to take thyroid hormones without medical indications. Factitious thyrotoxicosis, caused by T4 or T3 tablets, is entirely preventable. This also includes caution with illegal “fat burners” of unknown composition, in which thyroid hormones may be hidden.

The second factor is iodine. Adequate but not excessive intake reduces the risk of forming a nodular goiter, which with age can become toxic. At the same time, sudden large doses of iodine from seaweed, “detox” agents, or high-dose supplements can provoke thyrotoxicosis in people with already existing nodules.

The third factor is smoking. It is associated with a higher risk of Graves' disease and especially with the development and severity of endocrine ophthalmopathy. Quitting smoking is one of the few proven preventive recommendations in the guidelines regarding this disease (Kahaly et al., 2018).

• do not use T4/T3 and drugs of unknown composition for weight loss;
• use iodized salt, but do not take large doses of iodine on your own;
• quit smoking;
• with a family history of thyroid diseases — periodically check TSH.

Laboratory diagnosis

The first test when thyrotoxicosis is suspected is TSH. With an excess of thyroid hormones the pituitary sharply reduces its production, so TSH is usually suppressed — often below the detection limit. A normal TSH makes primary thyrotoxicosis unlikely.

Next, free T4 and total or free T3 are determined. An elevated T4 confirms overt thyrotoxicosis; in some forms an elevation of T3 predominates. If TSH is reduced but the hormones are normal, this is called subclinical thyrotoxicosis, which requires a repeat check after a few weeks.

To establish the cause, antibodies to the TSH receptor are determined: their presence indicates Graves' disease with high probability (Ross et al., 2016). If factitious thyrotoxicosis is suspected, thyroglobulin is useful — it is low when hormones are taken from outside and usually elevated with hyperfunction of the gland.

Before the tests it is important to stop supplements with high doses of biotin for at least a few days, because they give a picture similar to Graves' disease. Be sure to tell the doctor about all drugs, stimulants, and fat burners.

Instrumental studies

Ultrasound examination of the thyroid gland assesses its size, structure, and the presence of nodules. Doppler mapping shows the enhanced blood flow typical of Graves' disease and the reduced flow in destructive thyroiditis. This helps differentiate the causes without radiation exposure.

Scintigraphy with a radioisotope or an iodine uptake study shows whether the gland is actively capturing iodine. High diffuse activity is characteristic of Graves' disease, focal activity — of toxic nodules, and low activity — of thyroiditis and the intake of hormones from outside. The method has limitations and is not performed during pregnancy.

An electrocardiogram is recommended for all patients with thyrotoxicosis, especially athletes. It detects sinus tachycardia and, more importantly, atrial fibrillation, which may proceed asymptomatically. If there are heart complaints, the doctor may order Holter monitoring or echocardiography.

With pronounced or prolonged thyrotoxicosis it is advisable to assess bone mineral density, and with eye symptoms — to get a consultation from an ophthalmologist, since endocrine ophthalmopathy requires separate observation.

When to see a doctor

A scheduled visit to an endocrinologist is worthwhile if, over several weeks, an accelerated resting pulse persists, trembling hands, sweating, heat intolerance, insomnia, weight loss without a change in diet, menstrual cycle disturbances, or a feeling of “sand” in the eyes or their bulging have appeared.

An urgent consultation is needed for an irregular heartbeat, skipped beats, dizziness, shortness of breath at usual loads, chest pain, as well as a rapid enlargement of the neck. Such symptoms may indicate atrial fibrillation or other serious complications.

Emergency care is necessary if, against the background of thyrotoxicosis symptoms, a high temperature, a very rapid pulse, vomiting, diarrhea, agitation, or confusion arise — these are possible signs of a thyrotoxic crisis, which is life-threatening.

Until the doctor's conclusion, it is reasonable to give up intense training, stimulants, pre-workout complexes with caffeine, and training in the heat.

Treatment and return to sport

Three main approaches are used to treat hyperthyroidism: antithyroid drugs (thionamides), therapy with radioactive iodine, and surgical removal of the gland. The choice depends on the cause, the size of the goiter, the presence of ophthalmopathy, age, plans regarding pregnancy, and the patient's preferences (Ross et al., 2016; Kahaly et al., 2018). Thyroiditis often does not require specific treatment, only control of the symptoms.

For quick relief of heartbeat and tremor, beta-blockers are often prescribed. Athletes who compete should remember that beta-blockers are on the WADA Prohibited List in certain sports (in particular shooting and archery), so a therapeutic use exemption may be needed.

Antithyroid drugs have rare but serious side effects, in particular agranulocytosis. Therefore, during treatment, if a high temperature and a sore throat appear, you should urgently see a doctor and take a complete blood count.

A return to intense training is possible after achieving euthyroidism — normalization of the hormone level — and the absence of arrhythmias. The load is increased gradually, monitoring the pulse and well-being. Lost muscle mass and strength usually recover, while the state of the bones requires longer observation.

Editorial conclusions

It is impossible to fully prevent autoimmune hyperthyroidism, but the most common “sports” variant — factitious thyrotoxicosis from taking hormones — depends only on one's own decision. Quitting smoking and a sensible attitude toward iodine-containing supplements also reduce the risks.

Diagnosis is based on TSH, free T4 and T3, antibodies to the TSH receptor, ultrasound, and if needed scintigraphy; for an athlete an ECG is mandatory. Biotin should be stopped before the tests.

Disruptions in heart function, chest pain, or signs of a crisis require emergency care, and a return to full training is possible after the hormones normalize.

We also recommend reading our articles on the causes of hyperthyroidism in athletes, on the prevention of hypothyroidism, and on the ECG in sports medicine.

References

1. Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association guidelines for diagnosis and management of hyperthyroidism and other causes of thyrotoxicosis. Thyroid. 2016;26(10):1343–1421.
2. Kahaly GJ, Bartalena L, Hegedüs L, et al. 2018 European Thyroid Association guideline for the management of Graves' hyperthyroidism. Eur Thyroid J. 2018;7(4):167–186.
3. De Leo S, Lee SY, Braverman LE. Hyperthyroidism. Lancet. 2016;388(10047):906–918.
4. World Anti-Doping Agency. The World Anti-Doping Code: International Standard — Prohibited List. Montreal: WADA; чинна редакція.
5. U.S. Food and Drug Administration. Biotin (Vitamin B7): Safety Communication — may interfere with lab tests. FDA; 2017 (updated 2019).