Cortisol
Plain-English definitions of microbiome research vocabulary — the terms you'll see across articles, testing services, and probiotic claims.
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.
Related terms
HPA Axis
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.
Intestinal Permeability
The property of the intestinal lining that controls what passes from the gut into the bloodstream. Increased permeability (sometimes called "leaky gut") allows harmful substances to enter circulation, triggering immune responses.