Systemic inflammatory indices and the FT4/TSH ratio in Hashimoto’s thyroiditis: predictive and prognostic implications

To evaluate thyroid-related parameters and inflammation-derived hematological indices in patients with Hashimoto’s thyroiditis compared with healthy controls, and to assess their diagnostic performance across different thyroid functional states. This retrospective case–control study included 92 patients with Hashimoto’s thyroiditis and 92 healthy controls. Thyroid function tests, thyroid autoantibodies, inflammatory markers, and complete blood count–derived indices were analyzed. Patients were further classified as overt hypothyroid, subclinical hypothyroid, or euthyroid. Receiver operating characteristic (ROC) analysis and multivariable logistic regression were performed to assess diagnostic performance and identify independent predictors. Patients showed significantly altered thyroid hormone profiles and markedly higher thyroid autoantibody levels than controls (all p < 0.001). Among hematological parameters, erythrocyte sedimentation rate, monocyte count, hemoglobin level, and the lymphocyte-to-monocyte ratio (LMR) differed significantly, whereas composite indices such as the neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and systemic immune-inflammation index did not. Thyroid hormone–related parameters, particularly the FT4/TSH ratio, clearly distinguished clinical subgroups, while autoantibody and inflammatory indices were comparable across functional states. In multivariable analysis, the FT4/TSH ratio and LMR emerged as independent predictors of patient status. Routine laboratory ratios, especially the FT4/TSH ratio and LMR, provide complementary diagnostic information alongside established thyroid markers and may enhance clinical assessment of Hashimoto’s thyroiditis.