In our study, we evaluated the risk of disease recurrence in patients with papillary thyroid carcinoma (PTC), who were treated with thyroidectomy and RAI, by measuring serum Tg at different time-points: at least 40 days after surgery, in euthyroidism with TSH < 1.5 and usually 30 days before RAI (Tg−30), on the day of RAI (Tg0), and seven days after RAI (Tg+7). Here, TG is linked to differentiated thyroid carcinoma.