ABSTRACT
<p><b>OBJECTIVE</b>To investigate the relationship between interdigestive migrating motor complex (MMC) and plasma gastrointestinal hormones in patients with diarrhea or constipation-predominant irritable bowel syndrome (IBS) to elucidate the pathophysiology of IBS.</p><p><b>METHODS</b>A small intestine manometry was used to record the MMC cycles for at least 4-6 h in 19 IBS patients and 10 healthy volunteers. The plasma gastrointestinal hormone levels were examined according to altered MMC phases.</p><p><b>RESULTS</b>Compared with the healthy controls, IBS-D patients exhibited shortened duration of the small intestinal MMC cycle, prolonged phase III duration with greater amplitude, as well as faster propagation velocity, whereas the contrary alterations were found in IBS-C patients. The peak plasma motilin level occurred in phase III of the MMC cycle. The plasma somatostatin level was higher in IBS groups than in the healthy controls, but comparable between the diarrhea and constipation groups. Plasma 5-hydroxytryptamine showed periodical fluctuations with the phases of MMC cycles, reaching the peak level in phase II. IBS-D patients had higher 5-hydroxytryptamine levels than IBS-C patients and the healthy controls.</p><p><b>CONCLUSIONS</b>Plasma hormone levels are correlated with the MMC cycles, and the hormone level changes and small intestine motility disorder may play important roles in IBS pathophysiology.</p>