Risk and course of SARS-CoV-2 infection in patients treated for hypo- and hyperthyroidism

A novel coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread dramatically and has by the end of January 2021 affected over 100 million people, claiming more than 2 million lives. Hospital-based case series as well as population-based cohort studies have found that old age, male gender, and the presence of a wide range of comorbidities, such as hypertension, obesity, chronic obstructive pulmonary disease, and diabetes are the main risk factors for more severe disease and death due to SARS-CoV-2 infection.

During the first year of the pandemic, it has been unknown whether underlying hypo- or hyperthyroidism influence the risk of contracting and the subsequent course of SARS-CoV-2 infection. However, recent observations have provided important information, which should aid the physicians’ dialogue with their patients.

A limited-scale retrospective study conducted in the USA did not find hypothyroidism associated with an increased risk of COVID-19 related hospitalization or a poorer outcome, including death (van Gerwen M, et al. https://pubmed.ncbi.nlm.nih.gov/33013686/). A subsequent Danish nationwide register-based case-control (n = 2.428.687) and cohort study (n = 16.729) by Brix et al. (Lancet Diabetes Endocrinol, https://www.thelancet.com/journals/landia/article/PIIS2213-8587(21)00028-0/fulltext) showed that patients receiving treatment for hypo- or hyperthyroidism do not have an increased risk of contracting SARS-CoV-2 infection compared to a matched control population. Among infected individuals, there was no association between receiving treatment for hypo- or hyperthyroidism and 30-day mortality, risk of hospitalization, admission to an intensive care unit, need for mechanical ventilation, or renal replacement therapy.

The clinical implications of and recommendations following these findings is that receiving treatment for thyroid dysfunction should not per se impact the patients’ risk of acquiring SARS-CoV-2 infection, or the management of those who already contracted it.

While this information is based on large-scale national data, a number of issues remain to be clarified. Thus, whether etiology of the thyroid dysfunction, magnitude of thyroid dysfunction at time of infection, and cumulative time period of thyroid dysfunction, before or during infection, influence the risk and prognosis of SARS-CoV-2 infection is unknown. The study of larger cohorts of patients with a diagnosis of hypo- and hyperthyroidism will address the long-term consequences of SARS-CoV-2 infection for morbidity and mortality.

20 February 2021

The executive committee of the ETA