PSAT351 Thyroiditis following COVID-19 vaccination

BACKGROUND: COVID-19 vaccination has resulted in several unexplained side effects. However, thyroiditis has not been commonly reported. CLINICAL CASE: A 46- year-old woman without notable past medical history presented with new neck tenderness that began five days after the 1st Pfizer COVID vaccine. Symptoms progressed to nightsweats, heat intolerance, palpitations, mild tremors and fever of 101 F. Her neck tenderness was 4 out of 10 with muscle stiffness and 3 lb weight loss after receiving the vaccine. She took NSAIDS for fever every 12-24 hours. She denied any compressive symptoms, visual symptoms or sleep disturbances. She had no cough, sore throat or close contact with a COVID positive individual/sick contact. RT-PCR was done for COVID-19 and was negative. There was no personal history of radiation exposure or family history of Graves’ disease. There was no prior history of drug allergies. On examination, she was afebrile. Right thyroid gland was visible and tender to touch without overlying redness. A right thyroid nodule was appreciated without discrete margins and was not fluctuant. Left lobe was palpable without any nodules. She was tachycardic and had fine tremors on her hands. The remaining of the exam was unremarkable. Laboratory data showed TSH 0.01 mIU/L (0.3-5.50) with elevated FT4 of 3.05 ng/dL (0.76-1.70) and FT3 of 10.5 pg/mL (1.9-3.9). CBC showed a mild anemia with normal white blood cell count. ESR was elevated. TPO antibodies, thyroglobulin antibodies and Thyroid stimulating Immunoglobulins (TSI) were unremarkable but thyroglobulin level was significantly elevated at 1132 ng/mL (0-35). Thyroid scan demonstrated thyroiditis. Neck US showed diffusely heterogenous thyroid gland with asymmetric enlargement of the right lobe and isthmus and a new right exophytic thyroid nodule measuring 0.6×1.0×1.2 cm. Vascularity was not increased. Several non-enlarged lymph nodes were noted as well. Beta blockers was started in addition to NSAIDs. Neck tenderness resolved within 2 weeks. She received her second dose of COVID-19 vaccine as scheduled. Within 2 months of the initial presentation, thyroid functions normalized. Four months from the initial presentation, symptoms of mild hypothyroidism were noted with a TSH of 5.88. Levothyroxine 50 mcg daily was initiated. Repeat thyroid labs were normal. Follow up thyroid US showed resolution of the right exophytic thyroid nodule, and atrophic thyroid gland. She has remained on levothyroxine replacement with biochemical and clinical euthyroidism. CONCLUSION: Clinicians should be aware of thyroiditis as rare side effect of COVID-19 vaccine on thyroid gland. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.