The presence of thyroid peroxidase antibody of IgG2 subclass is a risk factor for thyroid dysfunction in chronic hepatitis C patients.

Objective: To investigate the prevalence of thyroid dysfunction (TD) and IgG subclasses of thyroid autoantibodies (TAs) and to determine the predictive factors of TD in chronic hepatitis C (CHC) patients. Design: Three hundred and twelve untreated hepatitis C virus-infected patients without a history of TD or treatment with thyroid hormones were enrolled in a cross-sectional study. Clinical and biological factors were statistically analyzed to determine the correlation between TD and this patient population. Results: The incidence of TD was 12.5% in CHC patients. Clinical hypothyroidism (5.8%) and subclinical hypothyroidism (3.8%) were more frequent than clinical hyperthyroidism (1.6%) and subclinical hyperthyroidism (1.3%). The percentage of TA-positive patients was significantly higher in people >60 years than in those ⩽60 years (31.9 vs 18.6%; P=0.042). Positive thyroid peroxidase antibody (TPOAb) was more frequent, and alanine aminotransferase (ALT) levels were lower in patients who displayed TD (TPOAb: 62.1 vs 10.8%, P=0.000; ALT: 43.5 vs 51 IU/l, PZ0.046). The positive percentage of TPOAb IgG2 subclass in the TD group was significantly higher than that of patients without TD (66.7 vs 16.7%, P=0.005). Multiple logistic regression analysis indicated that only TPOAb IgG2 subclass positivity was an independent risk factor for TD in CHC patients (odds ratioZ8; 95% CI: 1.225-52.246; P=0.030). Conclusions: TPOAb IgG2 subclass positivity is a risk factor for TD in CHC patients before antiviral treatment. IgG2 subclass of TPOAb might play an important role in the presence of TD in CHC patients. [ABSTRACT FROM AUTHOR]