What is Hypothalamic-pituitary-adrenal axis?
The hypothalamic-pituitary-adrenal (HPA) axis is the neuroendocrine system that controls the stress response by regulating cortisol production. It connects the brain’s threat detection systems to the body’s hormonal response.
How it works
When the brain perceives a threat, the hypothalamus releases CRH, which signals the pituitary gland to release ACTH, which triggers the adrenal glands to produce cortisol. Cortisol mobilizes energy, suppresses non-essential functions (immune, digestive, reproductive), and enhances alertness. The system includes negative feedback: cortisol signals the hypothalamus to reduce CRH production, terminating the response. In chronic stress, this feedback loop becomes dysregulated, producing persistently elevated cortisol that damages the hippocampus, cardiovascular system, and immune function.
Applied example
A student preparing for a final exam has a mildly elevated cortisol level that enhances memory consolidation and focus (adaptive stress response). A student with chronic academic anxiety has a persistently dysregulated HPA axis, producing cortisol levels that impair memory retrieval and sleep (maladaptive chronic stress).
Why it matters
The HPA axis is the primary mechanism through which psychological stress produces physical health consequences, making it the critical link between mind and body in stress-related disease.
