Fig. 1

The hypothalamic–pituitary–adrenal axis. Stress stimuli induce the production of CRH by the hypothalamus. CRH induces the production of ACTH by the pituitary gland which stimulates the production of glucocorticoids (cortisol) in the adrenal gland cortex. Cortisol acts on many cells, tissues, and organs including the immune system. The excessive release of cortisol as well as proinflammatory cytokines have a negative feedback on the central nervous system by inhibiting this circadian cycle. CRH corticotrophin releasing hormone, ACTH adrenocorticotrophin hormone