El–Salhy M, et al. – The authors aimed to investigate whether the densities of stem– and enteroendocrine cell progenitors were abnormal in the ileum of patients with irritable bowel syndrome (IBS) and whether any abnormalities in ileal enteroendocrine cells were associated with abnormalities in stem cells and enteroendocrine cell progenitors. They concluded that the abnormalities in the ileal enteroendocrine cells seemed to be caused by 2 mechanisms: decreases in the clonogenic activity of the stem cells and in the endocrine–cell progenitors differentiating into enteroendocrine cells, and switching on the expression of peptide YY (PYY) and switching off the expression of certain other hormones in other types of the enteroendocrine cells.