ACUTE EFFECTS OF INTERFERON-ALPHA ADMINISTRATION ON THYROID-HORMONE METABOLISM IN HEALTHY-MEN

Both hyper- and hypothyroidism have been reported during prolonged rec ombinant human interferon-alpha (rhIFN alpha) therapy. To assess the s hort term effects of IFN alpha therapy on thyroid hormone metabolism, we measured thyroid hormone concentrations in eight healthy volunteers for 24 h after sc administration of rhIFN alpha and, on another occas ion, after sc administration of saline (control study). There were no effects of rhIFN alpha on plasma T-4 and free T-4 or on thyroid hormon e binding index. However, rhIFN alpha induced a significant decrease i n the plasma concentrations of TSH (P < 0.03) and T-3 (P < 0.02) compa red with those in the control study, associated with an increase in rT (3) concentrations (P < 0.02). IFN alpha induced a moderate increase i n interleukin-6 (IL-6) concentrations (P < 0.02 us. control study), wh ereas IL-l and tumor necrosis factor concentrations remained below the detection Limit in all subjects. It is concluded that IFN alpha admin istration induces major changes in thyroid hormone metabolism, possibl y mediated in part by IL-6. The acute effects of rhIFN alpha mimic the euthyroid sick syndrome and appear to be different from the effects o f chronic rhIFN alpha treatment on thyroid hormone metabolism.