The FT4/FT3 ratio combined with thyroglobulin and parathyroid hormone for distinguishing benign from malignant thyroid nodules: a retrospective study based on histopathological diagnosis.

PURPOSE: To evaluate the diagnostic value of the FT4/FT3 ratio combined with other laboratory markers in distinguishing malignant from benign thyroid nodules. METHODS: This retrospective study analyzed 359 patients with thyroid nodules (142 benign, 217 malignant) based on histopathological results. Clinical and laboratory data, including FT3, FT4, FT4/FT3 ratio, thyroglobulin (TG), parathyroid hormone (PTH), and TSH, were collected. Statistical analyses included ROC curves and multivariate logistic regression. RESULTS: Malignant nodules showed higher FT4/FT3 ratios, TG, PTH, and TSH levels (p < 0.001). The FT4/FT3 ratio demonstrated moderate diagnostic accuracy (AUC = 0.708). TG and PTH had higher AUCs (0.750 and 0.776, respectively). Combining these markers improved the AUC to 0.896. Higher FT4/FT3 ratios, TG, and PTH were independent malignancy risk factors (p < 0.05). CONCLUSION: The FT4/FT3 ratio, combined with TG and PTH levels, enhances the differentiation of malignant thyroid nodules, offering a reliable diagnostic tool.