Interferon Treatment in COVID-19 Linked to Thyroid Changes

Nancy A. Melville

October 07, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

Dr David Lui

Treatment of COVID-19 with interferon beta-1b — even for just a few days, a much shorter period than is commonly used for maintenance in multiple sclerosis (MS), for example — is associated with potentially important adverse effects on thyroid function, according to research presented at the virtual 90th Annual Meeting of the American Thyroid Association (ATA).

"Our study is the first to report on the impact of interferon treatment on the thyroid in the context of COVID-19," first author David T.W. Lui, MBBS, of the Department of Medicine, University of Hong Kong, Queen Mary Hospital, told Medscape Medical News.

"If short courses of interferon treatment become a standard therapy for COVID-19, the modest changes detected thus far may indicate a phenomenon of clinical importance," he noted.

"As for now, our findings suggest that clinicians monitor the thyroid function and anti-thyroid antibodies among interferon-treated COVID-19 survivors and call for further follow-up studies regarding the clinical significance of these changes."

The study, also published in Frontiers in Endocrinology, involved 226 patients in Hong Kong who were treated for COVID-19 and had no known prior thyroid disorders.

Among those who received treatment with interferon, there were significant increases in anti-thyroid antibodies including anti-thyroglobulin (anti-Tg) and anti-thyroid peroxidase (anti-TPO) at 3 months compared with baseline, whereas no similar increases were observed among those not receiving interferon treatment.

In a multivariate analysis, treatment with interferon was found to be independently associated with a more than five-times greater odds of having a significant increase in anti-TPO titers at 3 months versus no interferon treatment (adjusted odds ratio [aOR], 5.73; P = .031).

"Interferon treatment for COVID-19, even for a short duration of a few days, could induce significant, though modest, increases in anti-thyroid antibody titers,' Lui reiterated.

Previous studies evaluating the effects of interferon on thyroid function in MS patients have shown that up to 33% of patients developed thyroid dysfunction and 20% developed thyroid autoimmunity, particularly during the first year of treatment, Lui and coauthors note in their study.

While the patients in the current study did not become symptomatic, the changes nevertheless could be indicative of further dysfunction and are important enough to warrant follow-up, Lui noted.

"Despite a modest magnitude of anti-TPO titer elevation among patients who developed incident anti-TPO positivity, further follow-up is warranted for potential subsequent thyroid dysfunction as the occurrence of anti-TPO can precede thyroid dysfunction," he noted.

Experience in MS Raises Thyroid Concerns

Interferon, a potent antiviral and anti-inflammatory agent, is well-established in the treatment of MS, often used over months or years as a maintenance therapy, and the drug has been repurposed in the age of COVID-19, where it has shown benefit as a much shorter-term, higher-dose treatment of just a few days, with benefits observed especially when initiated in the early stages of infection.

With increasing reports of thyroid effects after COVID-19 infection in general and known previous reports of incident thyroid dysfunction also associated with the use of interferon in MS, Lui and colleagues sought to evaluate if interferon treatment for COVID-19 affected thyroid function.

The study's 226 patients were treated at Queen Mary Hospital, in Hong Kong, for COVID-19 between July 2020 to January 2021. They were a median age of 55 and about half were men.

Most of the COVID-19 cases were mild (68.6%), 27% were moderate, and 4.4% were severe.

Among the patients, 135 (59.7%) received treatment with interferon for a median duration of 5 days (range 1-15 days) at a dose of 16 million IU/day, and 16.4% required dexamethasone.

Of note, patients treated with interferon had a higher SARS-CoV-2 viral load and more lymphopenia upon admission. And as ribavirin was given in combination with interferon, the interferon-treated patients were more likely to also be treated with that drug.

Overall, those treated with interferon showed a tendency towards having more abnormal function tests upon reassessment after 3 months (8.1% vs 2.2%; P = .08).

Further Evaluation of Those Who Had Full Details on Anti-Thyroid Antibodies

In a further evaluation of 179 patients who had full details on anti-thyroid antibodies, those who were treated with interferon (65.4%) showed significant increases in median anti-TPO levels, from 29.21 units at baseline to 34.30 units (P < .001) at the 3-month reassessment.

Likewise, the interferon-treated patients had median increases in anti-Tg titers, from 8.23 units at baseline to 9.14 units at reassessment (P = .001).

There were meanwhile no similar significant changes in those measures among those not treated with interferon.

Of the 179 patients, 143 were negative for anti-TPO at baseline, and 22 of these patients had significant interval increases in anti-TPO titers, defined as greater than 12 units, after 3 months.

Eight of these patients fully switched from being anti-TPO negative to positive, nearly all of whom (n = 7) were interferon-treated, with just one being interferon-naive.

There were no significant differences in disease severity, viral load, or lymphopenia between patients who did and did not have significant increases in anti-TPO titers, Lui noted.

Aside from interferon treatment, other factors found in the multivariate analysis to be independently predictive of a higher odds of having a significant increase in anti-TPO titers at 3 months included baseline C-reactive protein (CRP) levels (aOR, 1.59; P = .012) and higher baseline anti-TPO titers (aOR, 4.41; P = .001).

Evaluate Other COVID-19 Treatments for Thyroid Dysfunction?

Of note, the interferon dosing regimen used in the study of 16 million IU/day contrasts with the usual lower regimen of 8 million IU every other day as a chronic therapy in MS.

"Intriguingly, even with such a short duration of interferon therapy, we still observed a 5.6% rate of incident anti-TPO positivity at 3 months, which correlated with a higher chance of abnormal thyroid function tests during convalescence," Lui and coauthors add.

Amid ongoing efforts to disentangle the links between COVID-19 and thyroid dysfunction, the findings suggest importance in also considering COVID treatment, Lui noted.

"The thyroid risk has not been evaluated for other COVID treatments," he said.

The authors have reported no relevant financial relationships.

Frontiers Endocrinol. Published online September 30, 2021. Full text

90th ATA Annual Meeting. Abstract #22. Presented October 3, 2021.

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