Immunological relationship between autoimmune liver disease and autoimmune thyroid disease:a cross-sectional study

Background: High prevalence of autoimmune thyroid disease (AITD) in patients with autoimmune liver disease (AILD) has been observed. Data on the clinical relationship between AILD and AILD remain scanty. We aimed to evaluate the immunological relationship between AILD and AITD. Results: 324 patients with AILD were enrolled, 113 out of 324 patients were concurrent AITD (34.9%). Patients with autoimmune hepatitis (AIH) were more likely to develop AITD (45.8%), followed by autoimmune hepatitis-primary biliary cholangitis overlap syndrome (AIH-PBC OS) (39.5%) and PBC (22.6%). AILD patients with concurrent AITD showed higher levels of IgG (21.5 g/L vs 16.3 g/L, P<0.0001) and gamma globulin (γ-globulin)(27.1% vs 21.9%, P<0.0001), and IgG were positively correlated with thyroid antibodies [thymoglobulinantibody (TGAb), thyroid peroxidase antibody (TPOAb)] (r=0.396, 0.322; P<0.0001, P=0.002, respectively). The frequency of TPOAb positivity was highest in PBC patients with concurrent AITD (83.9%). The AIH concomitant with AITD had a higher nuclear homogenizing antinuclear antibody (ANA) positivity compared with the AIH alone (P=0.019). PBC patients with concurrent AITD were significantly older than the PBC patients without AITD (P=0.0004). Thyroid dysfunction in AILD patients with concurrent AITD was principally characterized by Hashimoto's thyroiditis (65.5%) and diffuse lesions were mainly indicated in thyroid ultrasound (53.1%). Conclusions: The high incidence of AILD concomitant with AITD, as well as the higher levels of serum IgG and γ-globulin, and the strong correlation between thyroid antibody and IgG, suggesting that we should strengthen the screening of autoimmune thyroid disease when diagnosing and treating autoimmune liver disease.