Reciprocal interactions between the GH/IGF-I system and cytokines

Abstract A growing body of evidence indicates a bidirectional relationship between the neuroendocrine system and immune functions. In this chapter we discuss the interactions between the growth hormone/insulin-like growth factor system and cytokines. Much experimental evidence suggests that both GH and IGF-I have a stimulatory effect on the immune response and on the production of immune (interleukin-2 and interferon-γ) and inflammatory (tumor necrosis factor, interlukin-1, interleukin-6) cytokines. However, the in vivo relevance in humans of these findings has yet to be fully demonstrated. On the other hand, proinflammatory cytokines affect the GH/IGF-I axis. These effects are relevant for the understanding of the mechanisms leading to stunted growth in chronic inflammatory diseases or diseases with recurrent infections in childhood.