Abstract
Coronavirus disease 2019 (COVID-19) has caused considerable morbidity, mortality, and poor outcomes worldwide. Thyroid hormones play a vital role in modulating metabolism and the immune system. Therefore, this study aims to identify the association between COVID-19 and hypothyroidism. A literature review was conducted using PubMed for study selection till April 2023. Keywords “Hypothyroidism,” “COVID-19,” and “Hypothyroidism” AND “Coronavirus” were used for the research process. All relevant articles evaluating the association between COVID-19 and hypothyroidism among adults were included. Information regarding the prevalence of hypothyroidism in COVID-19 patients, the association between COVID-19 and hypothyroidism, and poor outcomes among COVID-19 patients with hypothyroidism was retrieved from the eligible articles. Out of 303 articles, 12 were qualified for the final results, including 68,983 COVID-19 patients. There was heterogeneity in the results of the included articles. This systematic review found that hypothyroidism is prevalent among COVID-19 patients. Hypothyroidism, including subclinical hypothyroidism, may be associated with COVID-19 severity and outcome. In addition, pre-existing hyperthyroidism may correlate with poor COVID-19 outcomes. More research is needed to calculate the prevalence of hypothyroidism among COVID-19 patients, fully understand the mechanisms underlying this association, and identify effective strategies for managing COVID-19 in individuals with hypothyroidism.

Key words: COVID-19, respiratory infections, hypothyroidism, thyroid dysfunction, systematic review.