From hepcidin peptide analyses by quantitative LC-MS/MS, we found that hepcidin-25 levels in cell culture supernatants are increased by HCV infection (Fig 3A) and that hepcidin-25 levels in sera from hepatitis C patients are significantly decreased with HCV elimination by antiviral therapies (Fig 3B), reflecting the elevated expression of hepcidin mRNA due to HCV infection. The gene discussed is HAMP; the disease is hepatitis C virus infection.