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Thyroid Issues After COVID-19 Infection

Explore new research that suggests COVID-19 infections may cause temporary changes in thyroid test levels.
Thyroid Issues After COVID-19 Infection
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Article published December 8, 2021

The COVID-19 pandemic has impacted the economy, livelihood, and physical and mental well-being of people worldwide. Research continues to surface about its long-lasting impact on our health. 

You may see some confusing reports on COVID-19 related thyroid disorders show up after a COVID-19 infection. Ahead, a look at some research to understand the latest findings on the association between thyroid disease and COVID-19 infection.

New research shows COVID-19 infections may cause temporary changes in thyroid test levels


The onset of newly diagnosed thyroid conditions after having COVID is relatively well-established—primarily presenting as thyroiditis and temporary hyperthyroidism (overactive thyroid). However, new research finds that patients treated for hypothyroidism who then contract COVID can also have temporary changes in their thyroid test levels.


Italian researchers reported at the fall 2021 American Thyroid Association meeting on their study of a group of treated patients with hypothyroidism—a mix of patients with Hashimoto's thyroiditis (autoimmune thyroid disease) and total thyroidectomies—conducted in the first half of 2021. The researchers looked at the TSH (thyroid-stimulating hormone), Free T3, and Free T4 thyroid hormone levels pre- and post-COVID infection.


They found a transient increase in TSH levels after the infection in hypothyroid patients taking levothyroxine. In some cases, TSH levels nearly doubled. The increased TSH did, however, resolve over time.  


Interestingly, the TSH change was not accompanied by any measurable changes in the Free T4 and Free T3 levels, indicating that the circulating levels of thyroid hormone were stable.


These findings raise the possibility that hypothyroid patients may show artificially high TSH levels if thyroid blood tests are run in the period after a COVID infection. The risk is that in seeing an elevated TSH level, a physician might unnecessarily increase the thyroid hormone replacement dosage and potentially overmedicate the patient.


Researchers recommend that "endocrinologists should be aware of this event to avoid an unnecessary change in (levo)thyroxine dose."


> What can you do as a thyroid patient who's had a COVID-19 infection? 


If you're a thyroid patient who's had a COVID infection, advise the healthcare provider who monitors and manages your thyroid function. When evaluating your test results or adjusting your treatment dosage, you'll want your provider to take your COVID infection into account.


Understanding thyroiditis after COVID-19 infection


Several research studies conducted in 2021 found that a COVID-19 infection can lead to systemic inflammation of the immune system, leading to temporary hyperthyroidism and thyroiditis. In some cases, the new onset of thyroid disease is not autoimmune.


For example, researchers have found a higher rate of thyroiditis—inflammation of the thyroid gland—and low TSH levels in the hyperthyroid range in hospitalized COVID-19 patients during and after their active infection.


According to study author Ilaria Muller, MD, Ph.D., who presented her findings at the ENDO 2021 meeting, "SARS-CoV-2 seems to have multifactorial action on thyroid function."


Follow-up with groups of patients who had a COVID-19 infection shows that some continue to have an atypical form of thyroiditis months after their initial infection. In most cases, the thyroid levels normalize, but imaging tests still show thyroiditis.


This atypical thyroiditis differs from more common forms of thyroiditis in several ways. Unlike typical thyroiditis, this atypical post-COVID thyroiditis may:


  • Be less likely to be linked to neck pain
  • Affect men more than women
  • Be characterized by low TSH levels and low Free T3 levels, with normal or high Free T4 levels. (Low TSH and high Free T4 are not a typical combination.)


Researchers find that even three months after infectiona third of the patients still showed thyroiditis in imaging tests, even though thyroid function tests were normal and had no evidence of antibodies


Experts have concluded that the SARS-CoV-2 virus can damage the thyroid gland itself. "SARS-CoV-2 disease seems to trigger some dysfunction which very likely has complex and multifactorial mechanisms," Dr. Muller says. Unlike classical thyroiditis that can occur after a viral disease, including SARS-CoV-2, these patients have a different scenario indicating that something is happening within the thyroid with a different mechanism.


> What can you do if you had a COVID infection? 


If you had a COVID infection, it's a good idea to familiarize yourself with the range of symptoms of thyroid conditions, even if you have no prior medical history of thyroid disease. This is especially relevant if any thyroid abnormalities show up during the acute phase of the illness. You'll also want to be carefully monitored for thyroid symptoms and irregularities for at least a year after infection.

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Could you have a thyroid condition after a COVID infection? Start with this helpful quiz.



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Mary Shomon

Patient Advocate

Mary Shomon is an internationally-recognized writer, award-winning patient advocate, health coach, and activist, and the New York Times bestselling author of 15 books on health and wellness, including the Thyroid Diet Revolution and Living Well With Hypothyroidism. On social media, Mary empowers and informs a community of more than a quarter million patients who have thyroid and hormonal health challenges.

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