Usefulness of serum thyrotropin for risk prediction of differentiated thyroid cancers does not apply to microcarcinomas: results of 1,870 Chinese patients with thyroid nodules.

The objectives of this study were to investigate whether preoperative serum thyrotropin (TSH) concentrations can be used for risk prediction of differentiated thyroid cancers (DTC), in particular, microcarcinomas (DTMC), which may be in an early stage of development of DTC. The cohort of this retrospective study consisted of 1,870 patients who underwent surgery on thyroid nodules at a single hospital in an iodine-sufficient region in China. Serum TSH and anti-thyroid antibodies were measured and diagnoses were based on surgical pathology reports. Of 1,870 patients, 14.4% (n=269) had DTC. Eighty-nine DTCs were DTMC. As TSH increased, the prevalence of DTC rose clearly. The odds ratio in favor of having DTC with a serum TSH 1.9-4.8 mIU/L and > 4.8 mIU/L, compared with having a serum TSH 1.0-1.9 mIU/L were 1.57 (95% CI 1.03-2.40, P=0.038) and 5.71 (95% CI 2.31-14.14, P=0.0002), respectively. A similar pattern was yielded when excluding subjects with high thyroid autoantibodies. Higher TSH was also associated with lymph node metastasis and advanced disease (stage III and IV). However, preoperative TSH was 1.17 mIU/L in patients with DTMC vs. 1.08 mIU/L in patients with benign pathology (P = 0.80). The pattern of escalating prevalence with higher TSH did not apply to DTMC. In conclusion, serum TSH is not a good risk predictor of DTMCs. Elevated TSH level may be related to advanced stage, that is, progression of thyroid cancer, but not with the development of thyroid cancer, since microcarcinomas do not have any relation with TSH level.