We selected 92 patients without antithyroglobulin antibodies (TgAb), in whom thyroglobulin (Tg) after L-thyroxin withdrawal was undetectable (<1ng/ml) 6-12 months after initial therapy and who were considered to be at moderate / high risk for recurrence by this criteria: age >45 years; tumor size >1.5cm; and lymph nodes metastases in 43 (46.7%), local invasion in 26 (28.2%) or distant metastases in 23 (25%). Control whole-body scanning was negative in 78.2% of the cases and showed cervical uptake in the others. […]