COVID-19 and thyroid dysfunction: Study finds link

• The thyroid is a gland responsible for a variety of body functions, including metabolism, heart rate, and body temperature.
• Researchers from the University of Milan, Italy have found a link between thyroid dysfunction and moderate-to-severe COVID-19.
• Scientists also found evidence of thyroiditis in people with severe COVID-19 one year after infection, prompting the need for additional follow-up by healthcare providers.

Recent COVID-19 research has focused on how the disease impacts a person’s likelihood to develop other conditions, such as Parkinson’s disease, heart disease, and diabetes.

Now researchers from the University of Milan, Italy have found a link between thyroid dysfunction and COVID-19. And one year after infection, scientists found people with moderate-to-severe COVID-19 still had evidence of thyroid dysfunction.

The study was recently presented at the 24th European Congress of Endocrinology in Milan, Italy.

What is thyroid dysfunction? 

The thyroid is a gland located on the front of the neck. It produces specific hormones that help regulate a variety of body functions, including metabolism, body temperature, heart rate, and digestion.

Thyroid dysfunction occurs when something affects the thyroid, causing it to decrease or increase hormone production. There are four main types of thyroid disease:

• Hyperthyroidism happens when the thyroid produces too much thyroid hormone
• Hypothyroidism occurs when the thyroid does not make enough hormone
• Thyroiditis arises when the thyroid becomes inflamed, causing it to lower hormone production
• Hashimoto’s thyroiditis is an autoimmune disease where the body’s cells attack and damage the thyroid, causing lowered hormone production

Thyroid dysfunction diagnosis occurs through a combination of a physical exam, blood test, and imaging by a thyroid scan or ultrasound. Treatment varies depending on the type of thyroid disease a person has and can include medications, beta-blockers, radioactive iodine, and surgery.

COVID-19 and the thyroid

According to the study’s lead author Dr. Ilaria Muller, assistant professor in endocrinology, Department of Clinical Sciences and Community Health at the University of Milan, Italy, the purpose of the study was twofold.

One was to prove COVID-19 affected thyroid function and triggered inflammation of the thyroid, causing thyroiditis.

Dr. Muller explained COVID-19 modifies thyroid function on a variety of different levels, including, “non-thyroidal illness syndrome — a complex combination of adaptive and maladaptive mechanisms inducing transient alterations of thyroid function tests in severely ill people — cytokine storm, alterations of the hypothalamus-pituitary-thyroid axis, and by triggering an inflammation of the thyroid gland — thyroiditis.”

The researchers’ second goal was to correlate thyroid function with several parameters of COVID-19 disease severity. “We finally wanted to monitor the evolution of the thyroid dysfunction over time, up to one year after the SARS-CoV-2 infection, to verify the presence or absence of long-term consequences on the thyroid function,” she told MNT.

Dr. Muller and her team studied 100 patients admitted to the hospital for severe COVID-19. Upon analysis of their thyroid stimulating hormone (TSH) and other indicators, they found a frequent occurrence of thyroiditis in the patient population. However, the patients’ thyroids returned to normal levels shortly after recovery from COVID-19.

The researchers then examined the same patients 12 months later. They found regions of thyroiditis remained visible via thyroid ultrasound in half of the patient population.

Additionally, the scientists found four out of six patients had decreased uptake during thyroid of radiotracers such as technetium or iodine during thyroid scans. The decreased uptake is a hallmark of thyroiditis.

Future healthcare implications

Based on her team’s findings, Muller believed it would be useful for healthcare professionals to measure thyroid function in severe COVID-19 patients. This is because the serum concentrations of thyroid hormones TSH and free triiodothyronine (FT3) are prognostic indicators of thyroid disease severity.

“Furthermore, this would allow (them) to diagnose the possible presence of thyrotoxicosis — excess of thyroid hormones — due to atypical thyroiditis, an additional risk factor for a poor outcome in patients already debilitated by severe COVD-19 disease,” she explained.

Overall, Dr. Muller said the effects of SARS-CoV-2 infection and COVID-19 disease on thyroid function seem mild and transient.

“Even if the areas of thyroiditis within the thyroid gland persist for months after the infection, the thyroid function is promptly restored and no apparent increase of thyroid autoimmunity has been observed. Thus long-term consequences on the thyroid function are unlikely.”

– Dr. Muller

Dr. Antonio C. Bianco, professor of medicine at the University of Chicago, was also pleased to see that in most cases the function of the thyroid gland returned to normal after 12 months and that residual functional abnormalities were only present in a small number of people.

However, he told MNT that he did not expect to see ultrasonographic signs of thyroiditis in half of the individuals affected. “This suggests that the COVID-19-associated thyroiditis was severe in this population,” he added.

When asked how this research may impact the treatment of COVID-19 patients with thyroid issues in the future, Bianco said it warrants enhanced follow-up of these patients. “I would not be surprised if they were more likely to develop primary hypothyroidism after 5 or 10 years,” he added.

Additionally, Bianco noted for the next steps in this research he would like to see a larger follow-up. “Right now it seems that their thyroid function tests are normal and the ultrasonographic findings were the only abnormalities,” he explained.

“A longer follow-up, e.g. five or 10 years, would indicate if these residual ultrasonographic findings will be resolved and everything returned to normal or that some of these patients evolved to become hypothyroid.”

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