As an endocrinologist, one of the health conditions we see and treat is hyperthyroidism, which is when the thyroid gland becomes overactive and thyroid hormone levels become elevated.


During the COVID pandemic, I have noticed in my community-based urban practice that I have been seeing patients with hyperthyroidism, including diagnosing new Graves’ disease, more often than usual.  I have noticed this especially in the last few months, in the context of having the highest per capita rates of COVID-19 in all of Canada and USA in our province (as of early may 2021).


Backgrounder: the three most common causes of hyperthyroidism are:

  • Graves’ disease (an autoimmune condition)
  • Thyroiditis, where the thyroid becomes temporarily overactive, then settles down on its own (can be autoimmune, caused by a virus (sometimes called subacute thyroiditis), can be seen after pregnancy; other causes exist as well)
  • Hyperfunctioning thyroid nodules


A recent paper, published in the Journal of the Endocrine Society, reviewed published articles on the relationship between COVID-19 and thyroid disease.   Today we will focus specifically on COVID-19 and hyperthyroidism (many other aspects regarding the thyroid and COVID are covered in this article, for interested readers).


Studies began to emerge in late 2020, suggesting that elevated thyroid levels were common in people with COVID pneumonia and in the ICU with COVID-19, with 10-20% of patients having elevated thyroid hormone levels.  In the first study published, thyroid function tended to improve with improvement in infection-related symptoms, suggesting a thyroiditis type of picture. COVID infection has been associated with subacute thyroiditis in subsequent cases/series.


As discussed in the review, some case reports have now documented newly diagnosed Graves’ disease about 1-2 months following infection with the coronavirus.   Relapse of Graves’ disease (ie, Graves’ disease returning in people who had Graves’ disease in the past) has also been noted in about the same time frame after having a COVID-19 infection.


So how could COVID-19 infection cause hyperthyroidism?  The coronavirus uses ACE2 receptors to get into our cells. ACE2 is highly expressed in the small intestine, testicles, heart, kidney, lungs, and – you guessed it – the thyroid gland.  So, the coronavirus may have easy entry into thyroid cells, causing the thyroid cells to become inflamed and release thyroid hormone (thyroiditis).   It is also possible that the generalized inflammation triggered by the coronavirus may trigger autoimmune Graves’ disease.




There is emerging data to suggest that COVID infection may trigger the thyroid to become overactive.

It may be reasonable to monitor people who have had COVID infection for new thyroid disease or progression of pre-existing thyroid disease.

People who have had Graves’ disease in the past and who get COVID-19 should have thyroid function monitored.

Symptoms of hyperthyroidism to look out for include: palpitations, feeling hot, unexplained weight loss, tremors, muscle weakness, and diarrhea.

People who present with hyperthyroidism should be checked for COVID-19 infection.


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