Administration of interferon-gamma in healthy subjects does not modulate thyroid hormone metabolism

Cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL -2), IL-6, and interferon-alpha (IFN-alpha), alter human thyroid hormone me tabolism and may be involved in the pathogenesis the euthyroid sick syndrom e. Experimental data suggest that interferon-gamma (IFN-gamma) could be ano ther cytokine that might influence thyroid hormone metabolism. To evaluate whether IFN-gamma can be involved in the pathogenesis of the alterations in thyroid hormone metabolism in humans with nonendocrine illness, we measure d thyroid hormone concentrations in six healthy volunteers during 24 hours in a placebo controlled trial: once after subcutaneous administration of IF N-gamma (Immukine, [Boehringer Ingelheim GmbH, Ingelheim/Rheim, Germany] 10 0 mu g/m(2) subcutaneous) and once after the administration of saline (cont rol). In addition, we measured cytokine concentrations in plasma (TNF-alpha and IL-6). IFN-gamma did not induce effects on any of the measured thyroid hormone and thyroid-stimulating hormone (TSH) plasma concentrations. Moreo ver, IFN-gamma did not affect TNF-alpha plasma levels. Only a modest but si gnificant elevation of plasma IL-6 levels was detected after administration of IFN-gamma (p < 0.05 vs. control). It is concluded that IFN-gamma admini stration to healthy humans does not result in short term alterations of thy roid hormone metabolism. These data do therefore not support a role of IFN- gamma in the pathogenesis of the euthyroid sick syndrome in humans as might be deduced from in vitro and in vivo animal studies.