Abstract: Objective The present study sought to delineate alterations in thyroid function among patients with autoimmune hepatitis (AIH), with the ultimate aim of clarifying their potential role not only in the assessment of disease activity but also in the prediction of therapeutic response. Methods Seventy-eight patients diagnosed with AIH and admitted to Leshan Maternal and Child Health Hospital and Shaanxi Rehabilitation Hospital between August 2023 and June 2025, together with 50 healthy individuals who underwent routine examinations and served as controls, were included. Comparative analyses of thyroid functional indices were performed between patients and controls; subsequently, post-treatment evaluations were conducted, in which patients were stratified by disease severity and therapeutic response status. Results Before treatment, serum FT3 and FT4 levels in AIH patients were (4.1±0.4) pmol/L and (13.8±2.2) pmol/L, respectively, both significantly lower than those in the control group [(4.8±0.6) pmol/L and (15.9±2.7) pmol/L, P<0.05], while TSH was markedly higher [(3.7±0.8) mIU/L vs. (2.8±0.6) mIU/L, P<0.05]. In patients with severe disease, FT3 and FT4 levels [(3.9±0.4) pmol/L and (13.2±2.1) pmol/L] were significantly lower than those in patients with mild to moderate disease [(4.3±0.5) pmol/L and (14.2±2.4) pmol/L, P<0.05], whereas TSH was significantly higher [(4.0±0.9) mIU/L vs. (3.5±0.6) mIU/L, P<0.05]. Compared with patients with mild to moderate disease, histological inflammation grade <2, or liver fibrosis stage <2,patients with severe conditions, histological inflammation grade ≥2 or fibrosis stage ≥2 exhibited lower FT3 and FT4 levels and markedly elevated TSH levels (P<0.05). After treatment, 51 AIH patients (65.4%) achieved a therapeutic response. In the response group, FT3 and FT4 levels were (4.8±0.7) pmol/L and (15.8±2.7) pmol/L, respectively, significantly higher than those in the non-response group [(4.2±0.4) pmol/L and (14.0±2.2) pmol/L, P<0.05], while TSH was significantly lower [(2.8±0.5) mIU/L vs. (3.4±0.8) mIU/L, P<0.05]. Conclusion Characteristic alterations in thyroid function in AIH patients-alterations that appear to correlate with both the severity of hepatic involvement and the likelihood of treatment response-were identified. Such abnormalities may represent, rather than isolated endocrine derangements, a composite reflection of inflammatory activation, metabolic imbalance, and immune dysregulation. Taken together, indicators such as FT3, FT4, and TSH may thus not only carry prognostic implications but also serve as valuable predictors of therapeutic responsiveness.

Key words: Autoimmune hepatitis, Thyroid function, Treatment response, Hepatic inflammatory activity, Liver fibrosis