SARS-CoV-2 infection appeared to raise the risk for all forms of new-onset thyroid disease in people who needed hospital care due to COVID and those who did not, according to new data.

“If SARS-CoV-2 infection increases the risk of chronic thyroid dysfunction, the burden of thyroid diseases could rise substantially, with potential implications for healthcare systems by increasing the overall burden of diagnosis, follow-up, and treatment,” wrote Tim Q. Duong, PhD, a professor at the Albert Einstein College of Medicine in the Bronx, New York, and co-authors of the study published in The Journal of Clinical Endocrinology & Metabolism.

“Moreover, because thyroid dysfunction can adversely affect energy level, cardiovascular, metabolic, and neurocognitive health, its consequences may extend further,” they added.

‘Collateral Damage’

There’s a need to better understand how SARS-CoV-2 infection affects the body in the long term, particularly in the thyroid, said Duong, who is also the associate director of the Integrative Imaging & Data Science, Center for Health & Data Innovation, Montefiore Medical Center, Bronx. It’s possible that the immune system’s response to COVID may result in damage that will emerge in later years, he said.

Previous research has suggested several reasons why SARS-CoV-2 infection might trigger thyroid disease. A potential mechanism could be immune dysregulation, including excessive release of cytokines such as interleukin-6 and tumor necrosis factor-alpha (cytokine storm). This might trigger the development of thyroglobulin antibodies and thyroid peroxidase antibodies in previously unaffected individuals, the study authors wrote.

“The thyroid is susceptible to hyperinflammation,” Duong told Medscape Medical News. In COVID, the overregulated immune response — intended to kill SARS-CoV-2 — can overshoot. “In the process, there’s collateral damage.”

To assess these potential effects, Duong and co-authors conducted a retrospective cohort study using records from a large group of patients who had not been diagnosed with thyroid disease before the pandemic began. The researchers used data derived from electronic health records (EHRs) within the Montefiore Health System, collected between January 1, 2016, and August 17, 2024.

Their analysis focused on 15,372 individuals hospitalized with COVID, 41,757 people with a COVID diagnosis confirmed by polymerase chain reaction test who were not hospitalized, and a control group of 171,141 patients without a confirmed COVID diagnosis.

Overall, the researchers found that 2.99% of those hospitalized with COVID developed some form of thyroid disease, compared with 1.39% of those with a COVID diagnosis but no hospitalization, and 1.03% of the those without a recorded COVID diagnosis (P < .001).

These differences may be small in absolute terms but could signal significant future demand for thyroid treatment, the authors noted.

Compared with the control group, patients hospitalized with COVID had a significantly higher risk for all thyroid diseases (inverse probability weighting-adjusted hazard ratio [HR], 2.11 [2.03-2.19]), hypothyroidism (HR, 2.02 [1.92-2.12]), hyperthyroidism (HR, 2.31 [2.13-2.50]), and other/unspecified thyroid disease (HR, 2.27 [2.12-2.43]).

People who had COVID but were not hospitalized also had an increased risk for all thyroid diseases (HR, 1.40 [1.35-1.46]), hypothyroidism (HR, 1.37 [1.31-1.43]), hyperthyroidism (HR, 1.56 [1.45-1.68]), and other/unspecified thyroid disease (HR, 1.42 [1.34-1.51]).

Duong and co-authors acknowledged several limitations of their study. Results of at-home COVID tests were not included because these were not reliably documented in the EHR, so some patients classified as not having had COVID might have been infected, they noted.

“However, cases of severe [COVID] were unlikely to have been missed due to the need for inpatient admission, as Montefiore Health System is the predominant healthcare provider in the Bronx,” they wrote.

Montefiore’s hospitals serve an area that was an epicenter for the pandemic in its earliest days, admitting their first patient with COVID to an ICU on March 10, 2020. Within 2 weeks, there were 345 patients with COVID hospitalized at Montefiore hospitals.

Duong and co-authors also noted that Montefiore’s population has some key differences from the general US population. Recent US Census data estimate that 29% of people in the Bronx live in poverty compared with 11% of the overall US population.

Census data also show 42% of people in the Bronx identified as being only of White race compared with 75% of those in the general US population. And more than a third (34.6%) of Bronx residents are foreign born compared with 14% of those in the US population.

There needs to be more research in the general US population on the potential effects of COVID on thyroid conditions. Duong said he expects this will further establish the association seen in the Montefiore patients.

Risks for new thyroid disorders are greater in individuals who have preexisting conditions such as autoimmune disorders, obesity, and coronary artery disease, the study authors noted.

For clinicians, the Montefiore results should be a reminder to consider checking for thyroid disease in at-risk patients who have had COVID, even when their case was relatively mild.

“There are long-term effects of [COVID] on different organs that are subtle,” Duong said.

There was no outside funding for this research, and the authors reported having no financial disclosures.

Kerry Dooley Young is a freelance journalist based in Washington, DC. She has covered medical research and healthcare policy for more than 20 years.