Subacute thyroiditis in the SARS-CoV-2 era: a multicentre prospective study

Objective: Many cases of subacute thyroiditis (SAT) have been described related to SARS-CoV-2 infection, but no prospective data about follow-up are known. This prospective, longitudinal, 3-year, multicentre study aims to explore the clinical peculiarities and outcome of SAT in relation to SARS-CoV-2 infection, ascertained with antibody dosage. Methods: All patients receiving SAT diagnosis from November 2020 to May 2022 were enrolled. Data on anamnesis, physical examination, blood tests (TSH, freeT4, freeT3, thyroglobulin, anti-thyroid antibodies, C-reactive protein, erythrocyte sedimentation rate, complete blood count), and thyroid ultrasound were collected. At baseline, the presence of IgG against the SARS-CoV-2 spike protein or nucleocapsid was investigated. Patients were evaluated after 1, 3, 6, and 12 months. Results: Sixty-six subjects were enrolled. At baseline, 54 presented with pain, 36 (67%) for at least 15 days. Serum SARS-CoV-2 IgG measurements documented that 7 out of 52 subjects (13.5%) had infection before SAT diagnosis (COVID+). No significant differences between the COVID+ and COVID- groups were found at baseline, except for respiratory symptoms and fever, which were more common in COVID+ (P = 0.039 and P = 0.021, respectively). Among the 41 subjects who completed follow-up, COVID+ and COVID- did not differ for therapeutic approach to SAT or outcome, all having an improvement in neck pain, inflammation parameters, and ultrasound features. Conclusion: This is the first prospective study investigating any difference both at diagnosis and at follow-up between SAT presentation in patients with previous SARS-CoV-2 infection and those without. Our data demonstrate that SARS-CoV-2 does not impact on SAT onset, evolution, and outcome.