AUTOIMMUNE THYROID DISEASE: A RISK FACTOR FOR THYROID CANCER

Objective: To examine the relationship between clinical markers of autoimmune thyroid disease and the risk of thyroid cancer in patients with thyroid nodules. Methods: A retrospective cohort analysis was performed in a single clinical practice. In 2,500 consecutive patients, fine-needle aspiration biopsy (FNAB) was performed on all 3,658 ultrasonography-positive thyroid nodules that were >= 1.0 cm in diameter or >= 0.5 cm in diameter with ultrasound features suspicious for thyroid cancer. Serum concentrations of thyroglobulin antibodies (TgAb), thyroid peroxidase antibodies, and thyroid-stimulating hormone were measured before FNAB. Diagnosis of thyroid cancer was based on pathologic analysis of thyroidectomy tissue. Associations of thyroid cancer with the independent variables were determined by multivariate logistic regression analysis and reported as the adjusted odds ratio (OR) with the 95% confidence interval (CI). Results: There were 202 patients with malignant thyroid nodules, 51 patients with microscopic unsuspected thyroid cancer distal to the nodule under investigation (found at thyroidectomy), and 2,247 patients with benign thyroid nodules. To evaluate the association of clinical markers for autoimmune thyroid disease with thyroid cancer, we included all 253 patients with thyroid cancer in the malignant cohort. Thyroid cancer was associated with elevated levels of TgAb (OR = 1.57; CI = 1.11 to 2.23) and age <55 years (OR = 2.01; CI = 1.45 to 2.78), and a strong trend was demonstrated for association with male sex (OR = 1.45; CI = 0.99 to 2.12). Thyroid cancer was not associated with elevated levels of thyroid peroxidase antibodies. Conclusion: In patients who have thyroid nodules with indications for FNAB, elevated levels of TgAb are associated with thyroid cancer.