Alternating Hypothyroidism and Hyperthyroidism Complicated by Thyroid Eye Disease

This case study discusses a 70-year-old woman with a history of hypothyroidism who experienced alternating hypothyroidism and hyperthyroidism, complicated by thyroid eye disease (TED). Initially diagnosed with hypothyroidism in 2004, she became hyperthyroid in 2018, likely due to a shift from TSH receptor blocking antibodies to stimulating antibodies. Her condition was managed with methimazole and later levothyroxine, and her TED was treated with steroids and surgery. The patient has remained euthyroid since 2019. This case highlights the need for clinician awareness and further research into the mechanisms and treatment of alternating thyroid states.