RESUMO
Introduction: SARS-CoV-2 vaccines have been associated with thyroid dysfunction including thyroiditis and Graves' disease. We report a patient who developed thyrotoxicosis secondary to thyroiditis after COVID-19 mRNA booster dose vaccination. Case Description: A 74-year-old man with no known personal or family history of thyroid disorders went to his primary care physician with symptoms of palpitations. Of note, he had the first booster (third dose) of the Pfizer/BioNTech vaccine about 1 week before. He did not recall any similar symptoms after the first two doses of the same vaccine. There were no other symptoms of thyrotoxicosis such as hand tremors, weight loss or mood change. There was no family history of thyroid disorders. He was not on any medications such as amiodarone and was not taking any herbal supplements. He did not have any symptoms of upper respiratory tract infection. There was no neck pain. Physical examination was unremarkable with no goiter or thyroid eye manifestations. Thyroid function: free T4 elevated at 46.7 pmol/L (11.5-22.7) and TSH suppressed at 0.01 mIU/L (0.5-4.5). Thyroid stimulating immunoglobulin was positive at 200% (50-179). He was initially started on carbimazole 15mg daily. However, the patient became rapidly hypothyroid despite dose reduction and subsequent discontinuation of carbimazole with free T4 of 8 pmol/L and TSH of 36.4 mIU/L. An ultrasound of the thyroid gland showed vascularity with no discrete nodules. No thyroid uptake scan was done. The diagnosis was revised to thyroiditis post vaccination. Hypothyroidism persisted despite discontinuation of carbimazole before recovery 8 months later. Patient was well and did not require any thyroxine supplementation. Discussion(s): It is postulated that COVID-19 vaccines triggered thyroiditis via an autoimmune inflammatory syndrome caused by the vaccine adjuvants. A high index of suspicion is necessary and a thyroid uptake scan may be useful in making the diagnosis. Thyroiditis is a self-limiting condition and recognising it is important as no specific thyroid treatment is necessary in most patients. Patients should not be deterred from subsequent vaccination as COVID-19 infection has higher mortality risk than thyroiditis.Copyright © 2023