The influence of distant metastases on serum TSH elevation after L-T4 withdrawal in differentiated thyroid cancer

Abstract

Objective To investigate the influence of distant metastases on the increase rate (vx) of serum TSH and its change rate(Ra) in patients with DTC after thyroid hormone withdrawal (THW). Methods Three times or more serum TSH measurements were performed before and after THW in 97 patients (38 males, 59 females) who had underwent successful 131I ablation from January 2014 to July 2014. v1 (early period vx), v2 (later period vx) and change rate of v1 and v2 (Ra) were calculated and compared between M0 group (without distant metastases, n=67) and M1 group (with distant metastases, n=30). Two-sample t test and rank-sum test were used for statistical analysis. Results v1 in males was significantly higher than that in females ((3.58±2.13) vs (2.63±1.54) mU·L-1·d-1; t=2.549, P=0.012). v2 in M0 group was significantly higher than that in M1 group ((7.67±3.66) vs (3.68±4.33) mU·L-1·d-1; t=3.613, P=0.001). The difference of Ra between M0 group and M1 group was statistically significant(z=-4.17, P<0.05). Conclusions Distant metastases may affect the increase rate and its change pattern of serum TSH after THW. Serum TSH showed a slow elevation over time or even decline in patients with distant metastasis. Meanwhile TSH increased much higher over the THW time in most of the patients in M0 group. It was suggested that attention should be paid to the variation of serum TSH in DTC patients with distant metastases to avoid decrease of TSH during longer THW. Key words: Thyroid neoplasms; Neoplasm metastasis; Surgery, operative; Radiotherapy; Iodine radioisotopes; Thyroxine; Thyrotropin