[Melatonin secretion and metabolism in patients with irritable bowel syndrome]

Melatonin possesses enteroprotective proprieties. An action of a gastrointestinal motility modulator is also attributed to this hormone. Clinical investigations have proven that melatonin plays a role mainly in the pathogenesis of upper gastrointestinal tract disorders, much less data have been published on its action in intestinal disorders.

To evaluate melatonin (MEL) secretion and its metabolism to 6-hydroxymelatonin sulfate (6HMS) in patients with irritable bowel syndrome (IBS).

75 subjects, aged 18-52 years were included in this study. Three groups were distinguished: K (n=25)--healthy volunteers, IBS-D (n=25)--patients with diarrhoea predominant IBS, IBS-C (n=25)--subjects with constipation predominant IBS (IBS-C). IBS was diagnosed according to Rome III Criteria. Blood samples were taken from cubital vein at 2:00 a.m. and 8:00 a.m. on the next day. Concentrations of MEL in serum and 6HMS in 24-hour urine collection were determined by immunoenzyme ELISA method employing standard kits IBL nr RE59121 i RE59131).

The average melatonin concentration at 2:00 a.m. was found to be in the studied groups: K-55.3 +/- 6,6 pg/ml, IBS-D--57.5 +/- 16.7 pg/ml (p > 0.05), IBS-C--75.5 +/- .3 pg/ml (p < 0.01) and at 8:00 a.m. adequately--7.3 +/- 4.0 pg/ml, 14.9 +/- 8.9 pg/ml (p < 0.001) and 15.1 +/- 7.2 pg/ml (p < 0.001). 24-hour urinary 6HMS excretion amounted to: K--15.10 +/- 6.37 microg/ 24h, IBS-D--27.67 +/- 26.71 microg/24h (p < 0.05), IBS-C--31.47 +/- 29.19 microg/24h (p < 0.01).

Melatonin secretion in patients with IBS, especially in patients with IBS-C, is significantly increased compared with healthy volunteers. Melatonin metabolism in patients with IBS is not disturbed.