The treatment protocol is in accordance with current guidelines in Germany and includes total thyroidectomy (TT) with central lymphadenectomy (LNA), RIT to ablate the thyroid remnant, and TSH-suppressive therapy with L-thyroxine (TSH < 0.1 mU/l). RIT is administered under endogenous TSH-stimulation after 4 weeks’ cessation of L-thyroxine using standard activities of 1–4, and 1–2, GBq I-131 in patients with a 24-h-I-131 uptake below 10 % and 10–20 %, resp., or individual dosimetry aiming for at least 300 Gy in the thyroid remnant. If scintigraphic I-131 uptake by the thyroid remnant persists at whole-body scintigraphy (at least 200 MBq; at least 48 h) 3 months after RIT, a second fraction of RIT is given with 4–10 GBq.