Figure 1.

Acute and chronic hormonal response to stress. Normal physiological response to stressful stimuli leads to activation of the hypothalamic–pituitary–adrenal axis. This activation is characterized by hypothalamic release of corticotropin-releasing factor which elicits pituitary release of adrenocorticotropic hormone followed by the adrenocorticotropic hormone dependent release of cortisol and catecholamines. The production of corticotropin-releasing factor and adrenocorticotropic hormone is typically inhibited by negative feedback from increasing levels of catecholamines and cortisol. When exposed to chronic stressful stimulus, the normal physiological response is altered. The negative feedback mechanism is removed and the physiological system becomes oversensitive to stress. This leads to an increase in circulating stress hormones that compound rather than returning to homeostatic levels