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

Many cases of subacute thyroiditis (SAT) have been described related to SARS-CoV-2 infection, but no prospective data about follow-up is known. This prospective, longitudinal, 3-year, multicentre study is aimed at exploring clinical peculiarities and outcome of SAT in relation to SARS-CoV-2 infection, ascertained with antibody dosage. All patients receiving SAT diagnosis from November 2020 to May 2022 were enrolled. Data about 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 nucleocapside was investigated. Patients were evaluated after 1, 3, 6, 12 months. Sixty-six subjects were enrolled. At baseline, 54 presented with pain, 36 (67%) for at least 15 days. Serum SARS-CoV-2 IgG measurement documented that 7 out of 52 subjects (13.5%) had infection before SAT diagnosis (Covid+). No significant difference between Covid+ and Covid- groups was found at baseline except for respiratory symptoms and fever, more represented 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. 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.