Subacute thyroiditis after COVID-19 - Clinical, laboratory and ultrasound aspects

Subacute thyroiditis (SAT) is a self-limited inflammatory thyroid disease that follows or co-exists with a viral infection. COVID-19 has numerous multisystemic effects, including thyroid disorders. Possible mechanisms involved in COVID-19 infection-associated thyroid dysfunction include: apoptosis, inflammatory reaction and damage to follicular cells, direct effect of the virus, or interaction with thyroid angiotensin converting enzyme 2 (ACE2) receptors, respectively.

In the period November 2021-February 2022, 12 patients with SAT associated with COVID-19 were evaluated in our department (11 women, one man); mean age 50 ± 13.1 years. The mean time between COVID-19 infection and the onset of subacute thyroiditis was 23 ± 10.2 days. The most common symptoms presented by affected patients were: fever, pain in the thyroid, and complaints associated with thyrotoxicosis. All patients presented severe inflammatory syndrome, but the clinical and biochemical picture of thyrotoxicosis was more severe compared to other viral subacute thyroiditis. In 60% of cases, 2D ultrasonography was suggestive for subacute thyroiditis, but the parameters of Share-Wave Elastography (SWE) confirmed the diagnosis in 100% of cases (mean thyroid stiffness 234.2 ± 34.5 kPa). Under steroid therapy, during follow-up, thyroid stiffness gradually decreased at 4 weeks (130.38 ± 15.4 kPa), respectively, at 8 weeks (64.7 ± 5.3 kPa). The clinical outcome was favorable in all cases. Two patients developed hypothyroidism and were treated accordingly. SAT is characterized by a significantly increased stiffness of the thyroid.

The results of this study documented a significant difference in thyroid tissue stiffness between. SAT at baseline and values recorded at the follow-up visit. It should be noted that changes in the elastic properties of the thyroid parenchyma were associated with gradual normalization of biochemical parameters. The early diagnosis of SAT associated with COVID-19 is crucial, as prompt treatment with glucocorticoids leads to complete resolution of the disease.

SWE sonoelastography is useful in the positive diagnosis of subacute thyroiditis.