Long-Term Impacts of COVID-19 on Thyroid Health: Insights From Clinical Studies

Abstract

Background: COVID-19 emerged in December 2019 and rapidly became a global pandemic. It has since been associated with the progression of various endocrine disorders, including thyroid disease. The long-term effects of this interplay have yet to be explored. This review explores the relationship between COVID-19 and thyroid diseases, emphasizing thyroid gland function and the clinical implications for managing thyroid disorders in infected individuals.

Objectives: This narrative review intends to provide insight into the scope of research that future clinical studies may aim to address regarding the long-term effects of COVID-19 infection on thyroid health.

Methods: Keywords including "thyroid disease", "COVID-19", and "long-term" were used to search PubMed and Google Scholar for updated and relevant clinical research.

Results: COVID-19 affects the thyroid gland multifacetedly and includes direct viral invasion, immune-mediated damage, and hypothalamic-pituitary-thyroid axis disruption. Approximately 15% of COVID-19 patients experience thyroid dysfunction, which can present as thyrotoxicosis, hypothyroidism, or non-thyroidal illness syndrome (NTI). Noteworthy findings include inflammatory thyroiditis. Long-term effects, including those observed in children, include persistent hypothyroidism and exacerbated pre-existing thyroid-autoimmune conditions. Management of thyroid disorders in COVID-19 patients requires consideration: anti-thyroid drug (ATD) therapy used to treat hyperthyroidism in COVID-19 patients may need adjustment to prevent immunosuppression. Radioactive iodine (ROI) alternatives and interleukin-6 (IL-6) receptor antagonists could offer potential benefits and should be further explored.

Conclusion: Longitudinal follow-ups post-COVID-19 for patients with new and pre-existing thyroid disorders can improve disease outcomes. In addition, pathophysiological research on thyroid dysfunction in COVID-19 may help develop strategies to prevent and alleviate thyroid gland abnormalities post-COVID-19.

Keywords: clinical trials; covid-19; endocrinology; long-term; management; thyroiditis.

Figure 1. Effects of SARS-CoV-2 on pituitary function and the corresponding effect on its TSH secretion

TSH: thyroid-stimulating hormone

Figure 2. Pathophysiological methods of entry of SARS-CoV-2 and its associated systemic effects

RAAS pathway and HPT axis effects [11,12] RAAS: renin-angiotensin-aldosterone system; ACE-2: angiotensin-converting enzyme-2; TMPRSS2: transmembrane protease serine 2; TSH: thyroid-stimulating hormone

Figure 3. Thyrotoxicosis symptoms, diagnostic measures, and expected findings in patients presenting with thyrotoxicosis

Figure 4. Immune response involved in developing viral particle recognition by pediatric host cells and the associated effects on thyroid autoimmunity

B-cell and T-cell function [70]

Figure 5. First-line treatments of thyroid disorders during COVID-19, related side effects, and potential changes to these pre-existing regimens

The "X" through each red box represents a previously appropriate form of treatment for both hyperthyroidism and hypothyroidism that, when combined with COVID-19 infection, may produce adverse effects. Thus, the cross-outs represent incompatibility in the original treatment. The green boxes represent more suitable treatments for COVID-19 patients with a co-morbid thyroid disorder. IL-6: interleukin-6