A Rare Phenomenon of Hashimoto's Thyroiditis Converting to Graves' Disease

The document reported a rare case of a 67-year-old female patient whose Hashimoto's thyroiditis, initially diagnosed in 2015, converted to Graves' disease by 2018. Initially, she presented with symptoms of fatigue, cold intolerance, hair loss, and weight gain, and was treated with Levothyroxine. Over time, her Levothyroxine requirement decreased, and her symptoms resolved. However, she later developed symptoms of hyperthyroidism, including weight loss and periorbital edema, and was diagnosed with Graves' disease after laboratory tests and a thyroid ultrasound. She was treated with Methimazole and eventually underwent a total thyroidectomy, after which she resumed Levothyroxine. The case highlighted the importance of close monitoring and regular thyroid function tests, as the conversion from Hashimoto's to Graves' disease, though rare, could be mistaken for over-replacement of Levothyroxine.