Differentiated thyroid carcinoma (DTC) is the most frequent endocrine tumor, and its incidence has increased significantly in recent years . Total or near thyroidectomy and radioiodine ablation followed by thyroxine suppression of thyrotropin (TSH) is an effective and acceptable therapeutic scheme for most DTC patients [2,3]. The preferred drug of TSH suppressive therapy is levothyroxine (L-T4). L-T4 treatment reduces serum TSH level, thereby inhibiting the growth of residual neoplastic tissue, suppressing serum Tg level and reducing tumor recurrence and progression in DTC patients. However, excessive TSH suppression therapy can induce exogenous subclinical hyperthyroidism that may adversely affect the skeletal  and cardiovascular systems [5,6]. All those would affect the quality of life of patients with DTC. So far, there is still no consensus about the optimal serum TSH levels that is required for the initial treatment and follow-up of DTC despite several guidelines recommended the TSH suppressive levels. In high-risk patients who have persistent disease, the American Thyroid Association (ATA) and European Thyroid Association (ETA) recommend that the serum TSH level be kept at <0.1 mU/L. In higherrisk but disease-free patients, the ATA recommends TSH levels be kept at 0.1-0.5 mU/L for 5-10 years, whereas the ETA recommends TSH levels <0.1 mU/L for 3-5 years. In low-risk patients, the initial serum TSH levels should be kept at 0.1-0.5 mU/L in the ATA guidelines and <0.1 mU/L in the ETA guidelines. In low-risk and disease-free patients on follow-up, ATA and ETA both recommend serum TSH level be kept in the low normal range (0.3-2.0 mU/L) [7,8].