Design: This was a long-term (36 months) observational study. Methods: The investigators measured 24 h thyroid radioiodine uptake (RAIU) of 1.4 µCi (0.5 MBq) of 131-iodine at baseline and 24 h after intramuscular injection of 0.1 mg rhTSH in 42 patients (aged 42-80 years) who subsequently received 30 mCi 131-iodine 24 h after an identical rhTSH injection. Urinary iodine was measured at baseline and at 3 months after following a low iodine diet. TSH, free thyroxine (FT4), T3 (T3) and thyroglobulin (TG) were measured at baseline, 24 h, 48 h, 72 h, 168 h, one month, 3, 6, 9, 12, 18, 24 and 36 months after therapy. Thyroid volume was assessed by computer tomography at baseline and every 6 months thereafter.