• Subgroup of patients with differentiated thyroid cancer and intermediate-risk defined as follows according to TNM 2017:

‣ Papillary thyroid cancer (PTC) without aggressive subtype, follicular thyroid cancer (FTC) (with \< 4 foci of vascular invasion) or Hürthle cell carcinoma (HCC)

⁃ T1b or T2 with minimal extra-thyroid extension into the perithyroidal soft tissues and/or pN1 with largest nodal dimension between 2 and 10 mm, without extra-capsular invasion and with a number of metastatic nodes ≤ 10

⁃ T1aN1 with largest nodal dimension between 2 and 10 mm, without extra-capsular invasion and with a number of metastatic nodes ≤ 10

• Patient treated by total thyroidectomy with macroscopically complete tumor resection (R0 or R1) ± neck dissection

• Total thyroidectomy performed within 6 to 14 10 weeks before randomization

• Patient with or without anti-thyroglobulin antibodies (TgAb)

• No known distant metastases

• Normal post-operative neck ultrasound (US) or if doubtful US, negative cytology and normal Tg value (\<10 ng/ml) in FNA washout fluid

• Post-operative LT4 treatment initiated at least 6 weeks before randomization

• Performance Status 0 or 1

• Patients aged 18 years or older

• Signed informed consent form

• Patient who agrees to be followed annually during 5 years

• Patient affiliated to the French social security system