ObjectiveTo observe changing trend of thyroid hormones levels for postoperative patients with differentiated thyroid carcinoma,and to discuss the best therapeutic timing of thyrotropin (TSH) suppression. MethodsNinety-six patients with differentiated thyroid carcinoma from January 2011 to December 2013 in this hospital were selected.All of these 96 cases were divided into total thyroidectomy group (n=50) and thyroid lobectomy and isthmectomy group (n=46) according to the surgical approach.Serum thyroid hormones levels (T3,FT3,T4,FT4,and TSH) were detected on day 1,2,4,5,7,14 after operation. Results① In the total thyroidectomy group,the levels of T3 and FT3 elevated transiently on day 5,then decreased gradually,and which were lower than the low limit of normal range on day 14.The levels of T4 and FT4 elevated transiently,then reached the peak on day 2,and which started to decrease gradually and reached the low limit of normal range on day 14.The value of serum TSH decreased transiently,which started to increase rapidly on day 2 and surpassed the high limit of normal range on day 4,then continued to rise until on day 14.② In the lobectomy and isthmectomy group,the values of T3 and FT3 decreased gradually,then started to rise on day 5,and which were lower than preoperative values until on day 14.The values of T4 and FT4 elevated transiently and which reached the peak on day 2,and then gradually decreased,which appeared to be lower than preoperative values on day 14.The value of TSH decreased transiently,and which started to rise on day 4,then elevated gradually and exceeded preoperative level on day 7,which reached the high limit of normal range on day 14. ConclusionsThere are dynamic changes of thyroid hormones in postoperative patients with differentiated thyroid carcinoma.It is feasible to determine the best therapeutic timing of TSH suppression according to the levels of postoperative thyroid hormones.The best timing of thyrotropin suppression therapy is that TSH is above the high limit of normal range after operation.