CRH and irritable bowel syndrome: IBS is characterized by low-grade inflammation of the intestinal mucosa, mast cell and T cell infiltration, and proinflammatory cytokines in the ileocecum and colon.(12–16) Psychological stress and mucosal mast cells contribute to the pathogenesis of IBS, regardless of its subtypes.(17) In particular, stress induces gastrointestinal permeability through corticotrophin-releasing hormone (CRH) signaling, which stimulates the release of intestinal permeability mediators, such tryptase, from mast cells.