Endocrine Abstracts

Introduction: Subactue thyroiditis (SAT) is a self-limiting inflammatory condition caused by follicular destruction of the thyroid gland, commonly precipitated by viral upper respiratory tract infection 2 weeks preceding the onset of thyroid symptoms. However, SAT following COVID-19 vaccination is rare. Herein, we report two cases of subacute thyroiditis which presented after administration of COVID-19 vaccine.

Case series: The first patient was a 42 year old man who reported rapid onset of sore throat, neck pain and symptoms of thyrotoxicosis including weight loss, sweating and heat intolerance. The onset of symptoms was two weeks following his second dose of BNT162B2 mRNA (Pfizer-BioNTech) COVID-19 vaccine. There was no significant medical history and or prior use of medications that would precipitate thyrotoxicosis. He recovered well with a course of non-steroid anti-inflammatory agent. The second patient was a 31 year old lady, with no past medical history, who presented with neck pain and fever and symptoms of thyrotoxicosis three weeks after her third dose of BNT162B2 mRNA (Pfizer-BioNTech) COVID-19 vaccine despite having had two Sputik Covid V vaccine previously. She recovered well with a course of steroids. Both patients had negative TSH-receptor antibodies and thyroid peroxidase antibodies (0.20IU/ml, 0.39IU/ml). Imaging studies were consistent with thyroiditis with no obvious uptake noted on Technectium scan.

Discussion: SAT after vaccination, may develop as a result of direct injury by vaccine attributed by molecular mimicry. Due to the similarity between SARS-CoV2 spike protein and thyroid peroxidase, the cross reaction between the coronavirus spike protein with the TPO antibodies induce an autoimmune/inflammatory response to thyroid follicular cells. As with any form of SAT, treatment is symptomatic with non-steroidal agents and corticosteroids including levothyroxine if patient devloped hypothyroidism. In all these cases, association of SAT with the administered vaccines was suggested by temporal relationship between symptom onset and vaccination. Therefore, clinicians are encouraged to be vigilant of autoimmune diseases as possible complications of COVID-19 vaccination, even in patients with mild COVID-19 infections.

Conclusion: SAT can rarely occur following COVID-19 vaccination. Early identification of the possible endocrine side effects of the COVID-19 vaccine can help treat this condition. As SAT is a mild self-limiting illness, its possible association with prior vaccination should not deter people from vaccination.