Association of Hashimoto's thyroiditis with thyroid cancer.

This prospective study investigates the relationship between Hashimoto's thyroiditis (HT) and thyroid cancer (TC) in patients with thyroid nodules (TNs). We prospectively examined 2100 patients with 2753 TNs between January 5, 2010 and August 15, 2013. A total of 2023 patients with 2669 TNs met the inclusion criteria of TN ≥5 mm and age ≥18 years. Each patient had blood drawn before fine-needle aspiration biopsy (FNAB) for the following measurements: TSH, free thyroxine, free tri-iodothyronine, thyroid peroxidase antibody (TPOAb), and antithyroglobulin antibody (TgAb). Diagnosis of TC was based on pathology analysis of thyroidectomy tissue. The associations of TC with the independent variables were determined by univariate and multivariate logistic regression analysis and reported as adjusted odds ratio (OR) with 95% CI. A total of 248 malignant nodules were found in 233 patients. There was an association of TC with both increased serum TgAb concentration and age<45 years. An elevated serum TgAb concentration was found in 10.2% of patients (182 of 1790) with benign nodules as compared with 20.6% of patients (48 of 233) with malignant nodules (P≤0.0001). TgAb (OR=2.24: CI=1.57, 3.19) and TSH ≥1 μIU/ml (OR (95% CI)) OR: 1.49 (1.09, 2.03) were significant predictors of TC in multivariate analysis controlling for age and gender. TC was not associated with serum concentrations of TPOAb. In patients with TN, elevated serum concentration of TgAb and TSH ≥1 μIU/ml are independent predictors for TC. The association between HT and TC is antibody specific.