[Immuno-endocrine interactions at the hypothalamo-hypophyseal level]

The endocrine and immune systems are interrelated via a bidirectional network in which hormones modulate immune function and in turn, immune responses are reflected in endocrine changes. Stimulated immune cells produce cytokines and these substances have been shown to modulate the corticotroph, somatotroph, gonadotroph and thyreotroph axes. Interleukin-1, interleukin-6 and tumor necrosis factor alpha can either stimulate or inhibit the corticotroph axis by acting at all three levels, the hypothalamus, the pituitary gland and the adrenal glands. The hypothalamic effects of the cytokines are fast and mediated by the prostaglandins and by the nitric oxide (NO) pathway. In contrast, the cytokines at pituitary level have a slow onset of effect and their effects are not mediated by the prostaglandins or by the NO pathway. The immuno-neuroendocrine interactions are involved in numerous physiological and pathophysiological conditions. Thus, the interactions with the hypothalamo-pituitary-adrenal axis may represent an important feedback mechanism, through which the immune system by stimulating the production of immunosuppressive glucocorticoids avoids an overshoot of the inflammatory response.