A common type of chronic diarrhoea may be caused by a hormone deficiency, according to new research published in the November issue of Clinical Gastroenterology and Hepatology. The authors of the paper, from Imperial College London, with collaborators from King's College London and the University of Edinburgh, say their results could help more doctors recognise this type of diarrhoeal illness, and may lead to the development of more effective tests and treatments to help improve the lives of many people suffering with chronic diarrhoea.
Chronic idiopathic bile acid diarrhoea affects an estimated one in 100 people in the UK and it can cause people to have up to ten watery bowel movements a day, often for months at a time. This type of diarrhoea occurs when an overload of bile acid reaches the colon and causes excess water to be secreted into the bowel.
Today's study suggests that bile acid diarrhoea is caused by the body producing too much bile acid, because of a deficiency in a hormone called FGF19, which normally switches off bile acid production. The authors of the study say that new hormone-based treatments could be developed in the future to treat the condition and doctors could potentially test people's hormone levels to diagnose it.
Dr Julian Walters, lead author of the study from the Division of Medicine at Imperial College London, said: "Bile acid diarrhoea is a common condition, likely to affect more people than Crohn's disease or ulcerative colitis, yet until now we did not understand exactly what causes it. People with bile acid diarrhoea need to use the toilet urgently many times during the day and night. This can have a big impact on their lives, at home, at work and while they are travelling, as they always need to be near a toilet.
"If they are diagnosed, we have treatments that can remove bile acid from the colon, alleviate the symptoms and improve their quality of life. However, the current test used to diagnose the condition is not available in many countries and requires patients to attend the hospital twice. This means many people are not diagnosed. Our new findings mean that in the future doctors may be able to diagnose the condition by doing a quick and simple blood test," added Dr Walters.
Bile acid is produced by enzymes in the liver, to help the body digest fats. Its production is controlled by a hormone called Fibroblast Growth Factor 19 (FGF19). Over 90% of the bile acid is absorbed from the intestine back into the blood and is then reused. In healthy people, when bile acid is absorbed by the intestine, the body makes more FGF19 to stop new bile acid from being produced.
However, results of today's study suggest that people with bile acid diarrhoea make less FGF19, so the hormone 'switch' fails to stop the liver from producing more bile acid than the body needs. Because of this, more is produced than the intestine can absorb. This then irritates the colon and the resulting watery secretion causes diarrhoea.