Higher TSH Level is associated with Increased Risk of Malignancy in Thyroid Nodules

Background: To estimate the risk of malignancy of a thyroid nodule, several factors should be taken into account including age, gender, nodule size and history of radiation. Recently, preoperative serum thyroid stimulating hormone levels (TSH) is considered as an independent predictor for thyroid malignancies in patients with diffuse or nodular goiter; higher TSH levels are associated with an increased incidence of thyroid cancer in patients with nodular thyroid disease. We performed a diagnostic accuracy study on serum TSH in patients with malignant and benign thyroid nodules who were referred to the clinics of 5-Aazar and Shahid Sayad Shirazi Hospitals during the years 2014 and 2015. Methods: Patients with solitary thyroid nodules who were referred to Endocrinology clinics of 5-Aazar and Shahid Sayad Shirazi Hospitals during 2014 and 2015 were enrolled. Patients undergoing medical treatment were excluded. Serum TSH and T4 levels were initially measured in this study, and after performing fine-needle aspiration biopsy of thyroid nodules (FNA), pathology results were compared with TSH serum levels. Demographic information of participants was recorded. Chi-square test and independent T-test were used for data analysis. The P value ≤ 0.05 was considered statistically significant. Results: Of 80 patients, 24 (30%) were females with mean ± SD age of 42±13 years.  The mean ± SD serum TSH level in patients with malignant (N=20) and benign (N=60) nodules were 4.7±2.4 μU/mL and 2.5±2.3 μU/mL, respectively. All patients had subclinical thyroid dysfunction. In sensitivity analysis of ELISA, TSH level cut-point in the diagnosis of thyroid malignancies was 3.45 μU/mL with sensitivity and specificity of 80% and 78%, respectively. Sixteen (80%) of 20 patients in the malignant group had TSH levels above 3.45 μU/mL. In the benign group, 47 (78.3%) had TSH levels below 3.45 μU/mL. Conclusion: We found a significant difference in mean TSH serum level between patients with benign and malignant thyroid nodules; malignancy risk was higher in thyroid nodules from patients with high serum TSH level. The cut point for TSH in the diagnosis of thyroid malignancies is 3.45% with sensitivity of 80% and specificity of 78.3%.