Interferon-mediated fatigue.

Fatigue is a common side effect of interferon (IFN) therapy, reported in 70-100% of patients treated with IFN. The etiology of IFN-mediated fatigue (IMF) is multifactorial, with endocrine failure, neuropsychiatric disturbance, autoimmunity, and cytokine dysregulation potentially being contributors. Thyroid dysfunction, associated with the development of autoantibodies, is seen in 8-20% of patients receiving IFN-alpha. IFN-alpha also suppresses the hypothalamic-pituitary-adrenal axis. In addition, IFN-alpha therapy leads to depression and cognitive slowing, and depressed patients are predisposed to develop fatigue. Clinical management of IMF is challenging because the syndrome is variable in onset and severity and the pathophysiology is poorly understood. Current management typically centers on dose reduction, but ancillary nonpharmacologic measures may help improve symptoms. Other strategies include antidepressant or anxiolytic therapy and treatment of coexisting hypothyroidism. Future studies utilizing IFN should include quantitative guidelines for grading and managing IMF.