Frequently, patients with hepatitis C virus (HCV)
chronic infection have high levels of serum anti-thyroperoxidase and/or
anti-thyroglobulin autoantibodies, ultrasonographical signs of chronic
autoimmune thyroiditis, and subclinical
hypothyroidism, in female gender, vs healthy controls, or hepatitis B virus infected patients. In patients with "HCV-associated mixed
cryoglobulinemia" (MC+HCV), a higher prevalence of autoimmune thyroid disorders was shown not only compared to controls, but also compared to HCV patients without
cryoglobulinemia. Patients with MC+HCV or with HCV
chronic infection, show an higher prevalence of
papillary thyroid cancer than in controls, in particular in patients with
autoimmune thyroiditis. Patients with HCV
chronic infection, or with MC+HCV, in presence of
autoimmune thyroiditis, show higher serum levels of T-helper (Th)1 (C-X-C motif)
ligand 10 (
CXCL10) chemokine than patients without
thyroiditis. Probably, HCV thyroid
infection acts by upregulating CXCL10 gene expression and secretion in thyrocytes recruiting Th1 lymphocytes, that secrete
interferon-gamma and
tumor necrosis factor-alpha. These
cytokines might induce a further CXCL10 secretion by thyrocytes, thus perpetuating the immune cascade, that may lead into the appearance of autoimmune thyroid disorders in genetically predisposed subjects. A careful monitoring of thyroid function and nodules are recommanded in HCV patients.