Thyroid Function in the Time of COVID-19: A Systematic Review of Disease Progression and Vaccination Effect

Abstract

Objectives: This systematic review sought to address three key questions: (1) what differences in abnormal thyroid function test results are observed between COVID-19 patients and healthy individuals? (2) How does the severity of COVID-19 infection influence the development of thyroid dysfunction? (3) What impact do COVID-19 vaccines have on thyroid function and autoimmune processes? Methods: A literature search was conducted in PubMed, Web of Science, and Scopus from December 2019 to April 2023 to identify studies on thyroid dysfunction in COVID-19 patients without pre-existing thyroid conditions. The search focused on observational and case-control studies. Results: The literature search yielded 329 reports, from which duplicates and unrelated publications were excluded. Ultimately, 21 studies met the inclusion criteria and were selected for review. A second literature search yielded 605 reports, from which 5 studies were selected for inclusion in the systematic review. Conclusions: The findings suggest that SARS-CoV-2 infection can induce transient and reversible thyroid dysfunction, possibly through direct viral effects on the thyroid gland or via indirect immune-mediated mechanisms. Clinicians should be mindful of the potential, albeit rare, thyroid-related adverse effects of COVID-19 vaccines and monitor thyroid function, particularly in high-risk individuals.