Endocrine Abstracts

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic disease (Covid-19) has caused millions of deaths worldwide, thus a massive SARS-CoV-2 vaccination campaign has been launched since the end of 2020. Viruses and vaccines can induce adverse thyroid effects; SARS-CoV-2 infection and vaccines have been associated with several thyroid disorders, especially subacute thyroiditis (SAT) and Graves’ disease (GD). We aimed to study the occurrence of thyroid diseases following SARS-CoV-2 vaccination in our Centre.

Methods: From February 2020 onwards we have recorded all consecutive cases of SAT of any cause, noting if occurred shortly after SARS-CoV-2 infection or vaccines. We have also retrospectively extended this analysis to GD and Graves’ orbitopathy (GO). Our patients underwent blood tests for thyroid function, inflammatory markers, anti-SARS-CoV-2 antibodies and thyroid ultrasound scan.

Results: Up to December 2021 we have registered 15 patients with thyroid dysfunction occurring shortly after SARS-CoV-2 vaccination: 8 SAT and 7 GD, of which 3/7 (43%) also developed GO and 1/7 (14%) associated autoimmune acute hepatitis. Importantly, we observed an increased number of SAT diagnoses from June 2021 onwards, when the vaccination campaign was extended to the Italian general population. Patients’ mean age was 53 years (range 23-83 years) and females were 9/15 (60%). 3/15 (20%) patients had a previous history of thyroid disease (one subclinical hypothyroidism, one transient gestational hypothyroidism and one Hashimoto’s thyroiditis) and 10/15 (67%) patients had a positive family history of thyroid disorders. Patients received all SARS-CoV-2 vaccination types (8 Pfizer, 5 AstraZeneca, 1 Johnson&Johnson, 1 Moderna); symptoms were developed following the first dose (mean +15 days) in 10/15 (67%), the second (mean +6 days) in 4/15 (27%) and the third (mean +14 days) in 1/15 (7%) patients. A previous documented SARS-CoV-2 infection occurred in 4/15 (27%) patients several months before the vaccination.

Conclusions: SARS-CoV-2 vaccines seem to be associated with the onset of SAT or GD. Possible mechanisms involve the interaction of the spike protein with the ACE-II receptor expressed in thyroid tissue, a cross-reactivity of the spike protein with thyroid self-proteins or an immune reaction induced by adjuvants (ASIA syndrome). The majority of patients had a positive family history for thyroid disorders, thus a genetic predisposition is likely involved. Until more safety data about SARS-CoV-2 vaccines will be available, caution and strict monitoring of individuals predisposed to thyroid disorders or autoimmunity is suggested, especially those with low risk factors for Covid-19 disease.