TPO and Hashimoto thyroiditis: Evolution from Graves' disease to Hashimoto's thyroiditis is a common scenario but conversion is a rare occurrence that we observed in the presented case of a 56-year-old Hispanic female with a history of Hashimoto's thyroiditis with positive anti-thyroperoxidase (TPO) antibodies who was euthyroid on levothbefore75 μg for six years prior to her presentation to the emergency department (ED) with complaints of palpitations, exertional dyspnea, and unintentional weight loss of 20 lbs for four months.