Association between Serum Thyroid Stimulating Hormone Level and Papillary Thyroid Microcarcinoma in Korean Euthyroid Patients

Abstract

Received: 14 March 2011, Accepted: 23 June 2011 Corresponding author: Eui Dal Jung Department of Internal Medicine, Catholic University of Daegu School of Medicine, 3056-6 Daemyeong 4 -dong, Nam-gu, Daegu 705-718, Korea Tel: +82-53-650-4218, Fax: +82-53-651-4009, E-mail: jed15@cu.ac.kr Background: Thyroid cancer is a common disease and its prevalence is increasing. Recent reports have shown that an elevated thyrotropin (thyroid stimulating hormone, TSH) level is associated with thyroid cancer risk. However, the association between TSH level and thyroid cancer risk is not yet known for euthyroid patients diagnosed with papillary thyroid microcarcinoma (PTMC). Methods: Our study included 425 patients who underwent thyroid surgery and were diagnosed with PTMC between 2008 and 2009. Control group patients were diagnosed with benign nodules ≤ 1 cm in size by US-guided fine needle aspiration. Nodules with one or more suspected malignant-ultrasonographic feature(s) were excluded from this study. Patients who were not euthyroid or who took thyroid medication were also excluded. Results: The mean age of all patients was 48.5 ± 11.0 years and 88.8% were women. The mean age of those with PTMC was significantly lower than that of the control group. The mean TSH level was 1.78 ± 0.93 mIU/L, and the mean free T4 level was 15.96 ± 2.32 pmol/L. There was no difference in TSH level between the PTMC and control groups (1.77 ± 0.93 mIU/L vs. 1.79 ± 0.91 mIU/L, P = 0.829). After adjusting for age, TSH level was not correlated with tumor size (r = 0.02, P = 0.678) in the PTMC group. Moreover, the TSH level did not differ between patients with stage I and stage III-IV carcinoma (stage I, 1.77 ± 0.95 mIU/L; stage III–IV, 1.79 ± 0.87 mIU/L; P = 0.856). Conclusion: TSH levels are not elevated in euthyroid PTMC patients. Thus, further evaluation is needed before serum TSH can be used as a tumor marker for small nodules ≤ 1 cm in size in euthyroid patients. (Endocrinol Metab 26:297-302, 2011)