Androgen regulation of bowel function in mice and humans
Many digestive disorders have prominent sex differences in incidence, symptomatology, and treatment response that are not well understood. Irritable bowel syndrome (IBS), for example, affects approximately 10% of the population worldwide and tends to have different manifestations in males and females. Androgens are steroid hormones present at much higher levels in post-pubertal males than females and could be involved in these sex differences, but their normal functions in the bowel are largely unknown. Here, we show that gonadal androgens are required for normal gastrointestinal motility in vivo. In the healthy mouse gut, we detected androgen receptors in smooth muscle cells and a subset of enteric neurons. Surgical or genetic disruption of androgen signaling in adult mice selectively and reversibly altered colonic motility by affecting neurons rather than smooth muscle. To determine if androgens also influence human bowel function, we measured androgen levels in 208 adults with IBS. Free testosterone levels were lower in patients with IBS compared to healthy controls and inversely correlated with symptom severity. Taken together, these observations establish a role for androgens in the regulation of colonic motility and link altered androgen signaling with a common digestive disorder. These findings advance the fundamental understanding of gut motility, with implications for normal aging and disorders involving the gut-brain axis.