Evaluation of urinary 6-hydroxymelatonin sulphate excretion in women at different age with irritable bowel syndrome

Melatonin (MT) exerts a beneficial action in the treatment of many diseases, among them also in irritable bowel syndrome (IBS). Its secretion decreases with age, particularly, in the postmenopausal period in women. It has not been determined whether these changes can have an impact on the clinical picture of IBS. The study aimed at evaluating the urinary excretion of the main MT metabolite - 6-hydroxymelatonin sulphate (6-HMS) in women at different age with IBS. The investigations were carried out in five groups of 30 women each. Group Ia (the controls) - premenopausal healthy women (20-39 years), group Ib (the controls) - postmenopausal healthy women (46-66 years), group II - women with constipation predominant IBS (IBS-C; 19-42 years), group III - women with diarrhoea predominant IBS (IBS-D; 20-39 years), group IV - women with IBS-C (49-68 years), group V - women with IBS-D (48-69 years). The diagnosis of IBS was based on the Rome III Criteria after excluding other diseases. On the day of the study the patients remained on the same liquid diet (Nutridrink - 3x400 ml) and 1500 ml of still mineral water. 6-HMS concentration in urine was measured by ELISA method applying IBL antibodies (RE-54031, Immunological Laboratories). The results showed that 24-hour urinary 6-HMS excretion in the studied premenopausal women were as follows: group Ia - 15.13+/-5.83 microg/24 h, group II - 28.85+/-12.59 microg/24 h (p<0,01), group III - 26.10+/-11.76 microg/24 h (p<0,01) and in the postmenopausal subjects they were: group Ib - 10.66+/-3.23 microg/24 h, group IV - 13.73+/-5.09 microg/24 h ((p=0,02), group V - 21.39+/-10.88 microg/24 h (p<0,01). In women with IBS-C the obtained results of 24-hour 6-HMS urinary excretion were independent on the intensity of clinical symptoms. On the other hand, in women with IBS-D, both in the group III and V, higher intensity of ailments was accompanied by significantly increased 6-HMS urinary excretion. The results of the study allowed drawing the following conclusions: (1). 24-hour 6-HMS urinary excretion in women with the constipation-predominant (IBS-C) as well as the diarrhoea-predominant IBS (IBS-D) is higher than in healthy persons both in the premenopausal and postmenopausal period. (2). Relatively high 6-HMS urinary excretion in postmenopausal women with IBS-D indicates an adaptive increase in MT secretion from EC in the gut.