Endocrine Abstracts

Case report: A 52-year-old woman developed painful anterior neck swelling seven days after receiving the first COVID-19 vaccine AstraZeneca (AZ). Investigations showed TSH 0.14 mIU/l, CRP 34 mg/l and TRAb 0.3 IU/l. A neck Doppler ultrasound scan on day 15 showed features of thyroiditis. On day 21, she was hyperthyroid with TSH <0.02 mIU/l and free T4 70.3 pmol/l. COVID-19 test was negative, and she was advised to start Carbimazole and propranolol but took only the beta-blocker. She felt well seven weeks after vaccination, and her TSH was spontaneously normalised. Later, she remained asymptomatic but was biochemically mildly hypothyroid with TSH 11 mIU/l and free T4 9 pmol/l, and by week 18, her TSH had spontaneously normalised again. The diagnosis was subacute thyroiditis. She had no prior history of thyroid disease; she was otherwise well and took no regular medication. She was concerned that the COVID-19 vaccination had triggered her subacute thyroiditis.

Survey results: In light of this case report, we conducted an email survey via the Society for Endocrinology UK, about subacute thyroiditis arising within 28 days of administration of a COVID-19 vaccine. Seventeen cases were reported to us: seven were from the UK, 14 were from physicians, and three were from patients. Eleven cases followed Pfizer-BioNTech mRNA vaccine, five followed AZ ChAdOx1 S recombinant vaccine, and one occurred after Moderna mRNA vaccine. Nine cases developed after the first dose of vaccine and eight after a second dose, with symptom onset a mean of 14.5 days after vaccination, ranging from self-limiting to a more severe illness requiring glucocorticoid therapy.

Discussion: There was a temporal association between COVID-19 vaccination and the onset of subacute thyroiditis. It appears likely that COVID-19 vaccines can trigger subacute thyroiditis due to an autoimmune/inflammatory (ASIA) syndrome. Case reports and small case series of subacute thyroiditis following COVID-19 vaccination have recently been described. Endocrinologists should be aware of potential vaccine sequalae when managing thyrotoxic patients, including the heightened risk that thyrotoxicosis following COVID-19 vaccination will result from a potentially self-limiting subacute thyroiditis. It has also been reported that Graves′ disease can develop shortly following COVID-19 vaccination. With over 7 billion COVID-19 vaccine doses administered to date, and a background subacute thyroiditis incidence of 4.9 per 100.000, there remains a caveat that the cases reported here may have arisen by chance.