PYY and irritable bowel syndrome: The following five gastrointestinal endocrine cell types that secrete hormones that regulate appetite are abnormal in patients with IBS: ghrelin, cholecystokinin (CCK), peptide YY (PYY), enteroglucagon (oxyntomodulin) and serotonin (Table 1 and Figures 1, 2, 3, 4 and 5) [108-110,112-115,132,146-149].