Endocrine Abstracts

Background

We provided the first description of thyrotoxicosis due to atypical thyroiditis in patients hospitalised for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic disease (Covid-19), not associated with neck pain, more common in men, correlated with disease severity and coexisting with non-thyroidal illness syndrome. Classic viral subacute thyroiditis is often followed by permanent thyroid dysfunction and autoimmunity, thus we have started a longitudinal thyroid study, also including patients newly infected with SARS-CoV-2.

Methods

Baseline (at hospital admittance) and longitudinal (quarterly) study of patients hospitalised for moderate-to-severe Covid-19 disease, without known history of thyroid disorders, assessing serum thyroid function and autoantibodies, inflammatory markers and thyroid ultrasound scan (US). Patients showing US focal hypoechoic areas suggestive for thyroiditis also underwent subsequent thyroid ^99mTc or I¹²³ uptake scan.

Results

To date 185 Covid-19 patients have been studied, of whom 53 (29%) already evaluated at follow-up. At baseline, 44/185 (24%) had low serum TSH concentrations and 23/185 (12%) thyrotoxicosis (low TSH and/or high free-thyroxine). TSH positively correlated with lymphocyte count (0.38, P<0.001) but not with C-reactive-protein (-0.12, P = 0.09) and interleukin-6 (0.01, P = 0.936). Thyroid US performed during hospitalisation showed one or more focal hypoechoic areas suggestive for thyroiditis in 8/20 (40%) patients. At 3 months of follow-up the serum median (IQR) TSH concentrations were increased in all patients (n = 53) compared with baseline: 1.6 (1.0–2.2) mIU/l versus 0.9 (0.5–1.8) mIU/l, respectively (P<0.001). Serum free-thyroxine, free-triiodothyronine and inflammatory markers also normalised compared with baseline. Seven patients (13%) had positive anti-thyroglobulin (TgAb) and/or anti-thyroid-peroxidase (TPOAb) autoantibodies and were excluded from the thyroid imaging study. Thyroid US showed focal hypoechoic areas of thyroiditis in 14/46 (30%) patients; thyroid ^99mTc/I¹²³ scintigraphy resulted normal in 3/12 (25%), focally reduced in 8/12 (67%) and diffusely reduced in 1/12 (8%). The prevalence of thyroid focal hypoechoic areas at US was 53% and 27% in patients with low or normal TSH at baseline, respectively (P = 0.05). At 6 months of follow-up the thyroid function remained normal, no patients developed TgAb/TPOAb and the thyroid US and ^99mTc/I¹²³ scintigraphy studies are ongoing.

Conclusions

Thyroid dysfunction during moderate-to-severe Covid-19 disease is mild and transient, however atypical areas of focal thyroiditis at US persisted at 3 months in about one third of patients and long-term consequences are still unknown. The association of low serum TSH concentrations with both lymphocytopenia and focal areas of thyroiditis at US supports the hypothesis of thyroid gland involvement in SARS-CoV-2 infection.