Prevalence of HCV antibodies in autoimmune thyroid disease

Auto-immune thyroid disease (AITD) has often been reported during interferon-alpha therapy for chronic viral C hepatitis (HCV) or other diseases. Recently, a high AITD prevalence has been reported in HCV independently on alpha-interferon therapy. The aim of our study is to investigate the possible relationship between AITD and HCV and HBV virus infections, and their influence on the thyroid function.

We prospectively studied 112 patients with AITD (94 women and 18 men; mean age: 49.8 +/- 14.9 yrs) and 88 patients with non-toxic goitre (NTG) (73 women and 15 men; mean age: 50.2 +/- 13.5 yrs) as controls. In all patients HCV antibodies, HBsAg and anti-HBs antibodies, TSH, FT3 and FT4 serum levels, circulating anti-thyroid-peroxidase antibodies (TPO-Ab) and anti-thyroglobulin antibodies (TG-Ab) were measured.

HCV antibodies were positive in 11.6% of AITD patients (13/112) and in 2.3% of controls (2/88) (P < 0.05), the prevalence of HCV in the controls being similar to the expected value in the general population (about 2%). HBsAg and anti-HBs were found only in 2.6% of AITD patients (3/112) and 1.1% of controls (1/88) (P = NS), according to the expected value in the general population (about 2.5%). No difference in thyroid function was observed between positive and negative HCV subgroups.

A significant association between HCV infection and AITD was found. This finding confirms that HCV, but not HBV, could be one of the environmental factors responsible for the breakdown of immunological tolerance. Therefore detection of TPO-Ab and TG-Ab in all HCV patients, independently of IFN therapy, is suggested and the utility of a screening for HCV in all AITD patients is stressed.