PSAT319 A 34-year-old Male with Subacute Thyroiditis Following COVID-19 Vaccination: A Case Report

BACKGROUND: Few cases of subacute thyroiditis (SAT) have been reported after exposure to SARS-CoV-2 vaccines, which may stimulate immunogenic cross-reactivity in genetically susceptible individuals. Autoimmune/inflammatory syndrome induced by adjuvants (ASIA) should be considered as post-vaccination phenomenon, which may cause an underrecognized cause of autoimmune endocrine disease. CLINICAL CASE: A 34-year-old, Filipino male, presented with neck pain and throat discomfort, which started 5 days after his first dose of COVID-19 vaccine (Pfizer Bio-NTech mRNA vaccine). He reported sore throat, palpitations, easy fatigability, weight loss, diarrhea and mood changes. He had no recent history of any viral or respiratory illness. Premorbid, he was clinically and biochemically euthyroid. He had maternal history of thyroid carcinoma. Initial examination showed enlarged left thyroid nodule, tender on palpation. Laboratory work-up showed elevated C-reactive protein (8.16 mg/dL, n: 0.50 mg/dL), suppressed TSH (<0.005 uIU/mL, n: 0.27-4.20 uIU/mL) and elevated FT4 (89.15 pmol/L, n: 12-22 pmol/L), consistent with thyrotoxic phase of SAT. Thyroid peroxidase antibody, TSH receptor antibody and thyroglobulin were within reference range, while the thyroglobulin antibody was elevated (33.73, n: 4.11). SARS-CoV-2 RT-PCR was negative. Thyroid ultrasonography showed enlarged left thyroid lobe, with diffuse parenchymal disease and increased thyroid vascularity. Thyroid scintigraphy with 99mTc-pertechnetate demonstrated no tracer accumulation in thyroid beds and low thyroid uptake, consistent with thyroiditis. He was initially treated with nonsteroidal anti-inflammatory drug (Celecoxib) to relieve the neck discomfort and beta-blocker (Propranolol) to control his palpitations. Celecoxib was shifted to prednisone after 1 week due to further increase in FT4 (>100 pmol/L, n: 12-22 pmol/L), and persistence of neck pain. Prednisone was eventually tapered to discontinue when symptoms improved. Repeat thyroid function test after 4 weeks demonstrated results transitioning to the hypothyroid phase of SAT, elevated TSH (3.910 uIU/mL) and low-normal FT4 (15.71 pmol/mL). Levothyroxine was initiated at 25 g daily. After 4 weeks, repeat TSH was 3.75 uIU/mL. His levothyroxine dose was maintained and he remained well. Second dose of Pfizer Bio-NTech vaccine was administered when his thyroid status was stable, and he had no adverse effects thereafter. CONCLUSION: Thyroid dysfunction occurring after COVID-19 vaccination is probably an underreported adverse effect. To our knowledge, no case of thyroid dysfunction after COVID-19 vaccination had been reported yet in the Philippines. SAT should be considered in patients presenting with neck pain, fever and thyroid dysfunction. Awareness of potential thyroid dysfunction after administration of COVID-19 vaccine, in the context of safety monitoring, is important. REFERENCES: (1) Saygılı ES, Karakilic E. Subacute thyroiditis after inactive SARS-CoV-2 vaccine. BMJ Case Rep 2021;14: e244711. doi: 10.1136/bcr-2021-244711 Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.