Epidemiology, risk factors and prognosis of Interferon alpha induced thyroid disorders. A Prospective Clinical Study.

INTRODUCTION: Hepatitis C virus (HCV) infection is a worldwide problem and hepatitis, which is its natural unfavourable course, is still a challenge for hepatologist. At present, standards of treatment are changing from combined therapy with interferon alpha (IFN-α) and ribavirin to new antiviral drugs. The current classification divides interferon induced thyroid diseases (IITD) into two groups: autoimmune (Hashimoto disease, Graves disease, positive antithyroid autoantibodies in euthyroid patients) and non-autoimmune (destructive thyroiditis, non-autoimmune hypothyroidism). A common complication of cytokine therapy is the induction of antithyroid autoantibodies de novo without thyroid dysfunction. During therapeutic regimens combined with ribavirin, destructive thyroiditis with typical biphasic course is more common than in IFN-α monotherapy. Clinically, overt pathologies often have discrete symptoms, which cause diagnostic and therapeutic dilemmas.

AIMS: The aim of this study was to estimate IITD occurrence, to find risk factors for IITD development.

MATERIAL AND METHODS: The study group consisted of 66 patients treated for HCV infection. Before and during antiviral therapy, hormonal (TSH, fT4, fT3), immunological (thyroid autoantibodies), ultrasonographic and genetic (HLA-A2) parameters were evaluated.

RESULTS: Hormonal disturbances were detected in 24.2% of patients; however, 43.9% of patients had positive thyroid autoantibodies (de novo) without hormonal imbalance. Multivariate analysis revealed the following: female sex, elevated TSH level, occurrence of anti-TPO autoantibodies (TPO-Ab), and increased blood velocity in thyroid arteries are risk factors for IITD development.

IN CONCLUSION: Thyroid disorders are common during IFN-α therapy. Previous epidemiological data seem to be underestimated. Important risk factors for IITD development are: female sex, elevated serum TSH concentration (≥2.5 μU/mL), positive TPO-Ab and increased blood velocity in thyroid arteries.