Glossary
Hypothalamic-pituitary-adrenal axis
What is the hypothalamic-pituitary-adrenal axis?
The hypothalamic-pituitary-adrenal (HPA) axis is a communication system linking the hypothalamus in the brain, the pituitary gland and the adrenal glands. It helps regulate the stress response, including the release of cortisol.
How it works
The sequence begins when the hypothalamus releases corticotropin-releasing hormone (CRH). This prompts the pituitary to release adrenocorticotropic hormone (ACTH), which tells the adrenal glands to produce cortisol. Glucocorticoids affect energy use and provide feedback that helps regulate the response. Chronic stress can alter this regulation in different ways; it does not always produce persistently high cortisol.
Applied example
An approaching exam can activate this system, helping the body make energy available to meet a demand. But the student who feels most anxious does not necessarily have the highest cortisol level. Timing, prior stress and individual differences affect the response.
Why it matters
The HPA axis is one pathway connecting stress with physiological change. Its effects depend on context and interact with other neural, hormonal and behavioral processes.