Coronaviruses can directly affect certain endocrine glands, including the thyroid. The effects of COVID-19, specifically, on the thyroid have remained unclear since current research results have been conflicting. A recent British study sought to determine whether or not thyroid gland dysfunction is a common feature of COVID-19 patients, and if so, whether or not the effects continue after recovery.

What They Did

Participants in the study included adult patients admitted to Imperial College Healthcare in London with suspected COVID-19 between March 9 and April 22, 2020. Patients with pre-existing thyroid disease were excluded. Of the 456 patients, 334 had confirmed COVID-19, and 122 did not.

Measurements of thyroid-stimulating hormone (TSH) and FT4 (a hormone that makes up more than 90% of what is generally called ‘thyroid hormone’) were recorded at the time of admission and at the participants’ COVID-19 follow-up. Wherever possible, participants’ hormone levels from 2019 were used for comparison.

What They Found

The researchers found that:

• Most patients (86.6%) with COVID-19 had normal thyroid function. 
• None showed thyrotoxicosis (an excess of thyroid hormone in their bodies) or thyroiditis (inflammation or swelling of the thyroid gland).
• Only a few (0.6%) had hypothyroidism (an underactive thyroid). 
• Patients with COVID-19 had slightly lower TSH and FT4 at the time of admission than those without COVID. 
• In the COVID-19 patients with measurements from 2019, TSH and FT4 were both slightly lower at admission than in 2019. 
• TSH tests at baseline, admission, and follow-up showed that TSH returned to baseline levels after recovery from COVID-19.

What It Means

The study results indicate that thyroid dysfunction is not characteristic in patients with acute COVID-19 nor in COVID-19 survivors. While the researchers did see a statistically significant reduction in TSH and FT4 between baseline and admission, the reduction was still relatively minor and, according to the study authors, would not likely require treatment. 

*Khoo, B., Tan, T., Clarke, S. A., Mills, E. G., et al. (2021, Jan. 23). Thyroid Function Before, During, and After COVID-19. The Journal of Clinical Endocrinology and Metabolism. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823247/   

Much about the novel coronavirus, i.e., COVID-19, is still not fully understood. As research progresses and our knowledge of the virus increases, information can change rapidly. We strive to update all of our articles as quickly as possible, but there may occasionally be some lag between scientific developments and our revisions.