Enhanced stress responsiveness has been implicated as a potential mechanism contributing to the pathophysiology of irritable bowel syndrome (IBS).
This stress reposonse should be reflected in altered function of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system.
Both of these systems can modulate mucosal immune function.
Dr Chang and colleagues from California, USA characterized the basal circadian rhythm of adrenocorticotropin hormone and cortisol in irritable bowel syndrome vs healthy controls.
|Basal cortisol levels prior to a visceral stressor positively correlated with anxiety|
|Neurogastroenterology & Motility|
The team compared stimulated adrenocorticotropin hormone, cortisol and noradrenaline responses to a pelvic visceral stressor (sigmoidoscopy) in IBS and controls.
The research team correlated neuroendocrine responses with colonic mucosal cytokine expression and symptoms in irritable bowel syndrome.
The team conducted 2 separate studies in women.
In Study 1, basal cortisol levels were analyzed in 41 irritable bowel syndrome, and 25 controls using 24-hour collections of plasma adrenocorticotropin hormone and cortisol.
In Study 2, 10 irritable bowel syndrome patients with diarrhea, and 10 controls underwent sigmoidoscopy with measurements of stimulated neuroendocrine responses and cytokine mRNA expression in colonic tissue.
The researchers found basal adrenocorticotropin hormone levels were significantly blunted, while basal and stimulated plasma cortisol levels were higher in patients.
Basal cortisol levels prior to an experimental visceral stressor positively correlated with anxiety symptoms, but not irritable bowel syndrome symptoms.
The team found that irritable bowel syndrome patients with diarrhea had significantly decreased mRNA expression of mucosal cytokines in the sigmoid colon vs controls.
Dr Chang’s team concluded, “Although dysregulations in stress-responsive systems such as the hypothalamic-pituitary-adrenal axis and mucosal immune function are demonstrated in irritable bowel syndrome.”
“They do not appear to have a primary role in modulating irritable bowel syndrome severity and abdominal pain.”