A 15-year-old white girl presented with neck tenderness. On examination, a nodule was palpated in the right thyroid lobe. The neck was supple without abnormal lymphadenopathy. Eye findings related to Graves orbitopathy were absent. Weight, height, and blood pressure were unremarkable, but the heart rate was high at 104–114 bpm. The patient had a history of attention deficit hyperactivity disorder and was taking atomoxetine and fluoxetine. There was no history of childhood neck irradiation or family history of thyroid cancer. Several maternal relatives have acquired thyroid dysfunction.