This gut hormone could explain 40% of IBS-D cases—and lead to a cure

A mysterious gut hormone may be behind many cases of chronic diarrhea, especially in people with undiagnosed bile acid malabsorption, a condition often mistaken for irritable bowel syndrome. Researchers from the University of Cambridge identified that the hormone INSL5 spikes when bile acid reaches the colon, triggering intense diarrhea. Their discovery not only sheds light on the biological cause of symptoms but opens the door to a diagnostic blood test and new treatment options, including a surprising existing drug that blocks this hormone’s effects.