Thyroid dysfunction in COVID-19

The COVID-19 pandemic has affected over 772 million people globally. While lung damage is the major contributor to the morbidity and mortality of this disease, the involvement of multiple organs, including the endocrine glands, has been reported. This Review aims to provide an updated summary of evidence regarding COVID-19 and thyroid dysfunction, incorporating highlights of recent advances in the field, particularly in relation to long COVID and COVID-19 vaccination. Since subacute thyroiditis following COVID-19 was first reported in May 2020, thyroid dysfunction associated with COVID-19 has been increasingly recognized, secondary to direct and indirect effects on the hypothalamic-pituitary-thyroid axis. Here, we summarize the epidemiological evidence, pattern and clinical course of thyroid dysfunction following COVID-19 and examine radiological, molecular and histological evidence of thyroid involvement in SARS-CoV-2 infection. Beyond acute SARS-CoV-2 infection, it is also timely to examine the course and implication of thyroid dysfunction in the context of long COVID owing to the large population of survivors of COVID-19 worldwide. This Review also analyses the latest evidence on the relationship between the therapeutics and vaccination for COVID-19 and thyroid dysfunction. To conclude, evidence-based practice recommendations for thyroid function testing during and following COVID-19 and concerning COVID-19 vaccination are proposed. COVID-19 has been linked to an increase in thyroid dysfunction among current and past patients. This Review discusses and evaluates the evidence for COVID-19 causing thyroid dysfunction, including after COVID-19 vaccination and during long COVID. The prevalence of abnormal thyroid function is around 15% in patients with COVID-19 and most commonly presents as non-thyroidal illness syndrome.SARS-CoV-2 can affect the thyroid directly or indirectly, possibly resulting in subacute thyroiditis and autoimmune thyroid disorders.Patients with pre-existing thyroid dysfunction do not appear to be at higher risk of adverse outcomes related to SARS-CoV-2 infection than members of the general population.Follow-up studies of survivors of COVID-19 in the past 2 years show no major long-term sequelae from SARS-CoV-2 infection on the thyroid.COVID-19 vaccination might be associated with subacute thyroiditis and Graves disease, although this is very uncommon, and COVID-19 vaccination is otherwise not associated with major changes in thyroid function and autoimmunity.Patients with pre-existing thyroid dysfunction can safely receive COVID-19 vaccination.