Biological Pathway
HPA Axis
Last updated
The hypothalamic-pituitary-adrenal axis. The hypothalamus releases CRH, the pituitary responds with ACTH, and the adrenal glands release cortisol, which acts on metabolism, immune function and the brain before feeding back to shut the sequence off. Output follows a daily rhythm, high in the morning and low at night, with acute stress responses layered on top.
Why it matters here
Because output is rhythmic, a single cortisol figure means very little without the time it was drawn, which undercuts most before-and-after claims about stress hormones.
What it is not
One letter apart from the HPG Axis and routinely swapped for it: HPA ends at the adrenal glands and cortisol, HPG at the gonads and the sex hormones. Adrenal fatigue is not an HPA finding and is not what this term means.
Also called
- hpa
- hypothalamic-pituitary-adrenal
- stress axis
Stress axis is the informal name, though the axis runs continuously and regulates far more than the stress response.
Compounds carrying this term
None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.