Figure 2.

Schematic representation of the hypothalamic-pituitary-adrenal (HPA) axis. In response to stimulatory neural input from other brain regions (e.g., in stressful situations), certain cells in the brain’s hypothalamus secrete corticotropin-releasing hormone (CRH). This hormone stimulates cells in the pituitary gland, which is located below the hypothalamus, to secrete adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH then is transported to the adrenal glands located atop the kidneys, where it activates certain cells to release cortisol, which exerts numerous metabolic effects. The HPA axis is regulated by both direct and indirect negative feedback mechanisms. Thus, cortisol directly inhibits further release of CRH from the hypothalamus and ACTH from the pituitary gland and indirectly lowers CRH secretion by reducing the neural input from other brain regions.

NOTE: + = stimulatory effect; –= inhibitory effect.