Abstract: Objective To explore the prevalence of thyroid dysfunction in patients with chronic hepatitis C during pegylated interferon（Peg-IFN） combined with ribavirin（RVB） therapy and its impact on antiviral efficacy. Methods 204 patients （HCV 1b infection in 173,2a in 9,3b in 2,and undefined in 20） with chronic hepatitis C who had normal thyroid function at the beginning of the study received the treatment of Peg-IFN combined with RBV. The regimen lasted for 48 weeks for patients with HCV 1 and undefined genotypes,and for 24 weeks for patients with genotype 2 and 3. Serum FT3,FT4,sTSH,Tg-Ab,TPOAb and TRAb were detected. Results Thyroid dysfunction occurred in 43 patients（19.0%） during the PEG-IFN/RBV treatment,among whom 16.3% presented with hypothyroidism,39.5% with subclinical hypothyroidism,25.6% with hyperthyroidism,and 18.6% with subclinical hyperthyroidism. Thyroid dysfunction mainly occurred at 24 to 36 week treatment. At the end of observation,37 patients with thyroid dysfunction recovered spontaneously or after medical intervention,however,six patients with high serum titer of thyroid autoantibodies still needed close monitoring of thyroid function and sustained administration of anti-thyroid agents. There were no significant differences as respect to RVR,EVR,ETVR and SVR between 43 patients with thyroid dysfunction and 161 with normal thyroid function（P>0.05）. Conclusion Thyroid dysfunction occurs in patients with chronic hepatitis C during Peg-IFN/RBV treatment. The thyroid dysfunctions are reversible,and do not influence the antiviral efficacy.

Key words: Hepatitis C, Thyroid function, Pegylated interferon, Virologic response