TG and neoplasm: As far as the justification for this approach is concerned, all the above-mentioned guidelines mainly refer to two literature sources [88,89], according to which a 98–99.5% probability of a tumor-free status can be assumed if the TSH-stimulated Tg (s-Tg) value is below a defined cut-off (0.5 ng/mL in the BTA guideline, 1.0 ng/mL in the ATA guideline); in this case, further follow-up care may be limited to basal Tg measurements and high-resolution neck ultrasonography every 6–12 months.