123I Scintigraphy Mirror Image of Graves Disease Induced by Radioiodine Treatment for Toxic Adenoma

A 61-year-old woman presenting with hyperthyroidism received 131I therapy for a toxic adenoma diagnosed by 123I scintigraphy. Six months later, the patient had a relapse of hyperthyroidism, and 123I scintigraphy showed a mirror image of the first scintigraphy: a high and diffuse uptake in the thyroid gland except for the previously treated nodule. Graves disease was confirmed by elevated thyrotropin receptor antibodies. The patient was cured by a second radioiodine therapy. Radioiodine-induced Graves disease may occur within 6 months of 131I treatment of toxic adenoma and can be treated with a second line of 131I.