Recurrent Graves' hyperthyroidism after prolonged radioiodine-induced hypothyroidism

Background: Radioactive iodine (RAI) is the most cost effective therapy for Graves' disease (GD). Patients with GD who have become hypothyroid after therapeutic RAI, rarely develop recurrence of disease. Herein we describe a case of recurrence of thyrotoxicosis after 2 years of hypothyroidism. Methods: We present the clinical features, laboratory findings, imaging and management of an unusual case of recurrent hyperthyroidism. Results: A 48-year-old male presented to the emergency room with a 2-day history of palpitation, chest discomfort and 30 pounds of weight loss. Examination was remarkable for rapid and irregular pulse, diffuse thyromegaly and brisk deep tendon reflexes but no eye changes or tremors. Laboratory tests showed thyroid-stimulating hormone (TSH) of <0.004 (0.3-5.6 mIU/ml), free thyroxine (FT4) 4.96 (0.9-1.8 ng/dl), free triiodothyronine (FT3) >20 (1.8-4.7 pg/ml), total thyroxine >800 (80-200 ng/dl). Electrocardiogram showed atrial fibrillation with rapid ventricular response. RAI uptake and scan showed a homogenous gland with 54% uptake in 6 h and 45% in 24 h. He was treated with propranolol and propylthiouracil with some clinical improvement. He subsequently underwent RAI therapy and developed hypothyroidism after 8 weeks. Hypothyroidism was treated with levothyroxine. At 2 years after RAI ablation, he again developed symptoms of hyperthyroidism and had suppressed TSH. The levothyroxine dose was stopped, 3 weeks after discontinuing levothyroxine, he remained hyperthyroid with TSH of 0.008 and FT4 of 1.62 and FT3 of 4.8. RAI uptake demonstrated 17% uptake at 24 h. Conclusion: Recurrent hyperthyroidism in GD is uncommon after development of post-ablative hypothyroidism. Our case illustrates the need for continued surveillance.