HPA Axis
Plain-English definitions of microbiome research vocabulary — the terms you'll see across articles, testing services, and probiotic claims.
The hypothalamic-pituitary-adrenal axis — a neuroendocrine system that regulates the body's stress response. When activated, it triggers cortisol release, which affects gut motility, intestinal permeability, and microbial composition. Chronic HPA axis activation is implicated in IBS and other gut disorders.
Related terms
Cortisol
The primary stress hormone produced by the adrenal glands in response to HPA axis activation. Chronic cortisol elevation can increase intestinal permeability, alter gut motility, reduce mucus production, and shift the composition of the gut microbiome toward less diverse states.
Gut-Brain Axis
The bidirectional communication system between the gastrointestinal tract and the central nervous system, involving neural, hormonal, and immune pathways. The microbiome plays a central role in this communication.