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. Author manuscript; available in PMC: 2021 Oct 1.
Published in final edited form as: Am J Gastroenterol. 2020 Oct;115(10):1596–1603. doi: 10.14309/ajg.0000000000000696

Figure 1. A graphical representation of the enterohepatic circulation.

Figure 1.

Left panel indicates bile acid circulation in healthy individuals. Bile acids are reabsorbed in the ileum, activate FXR and increase FGF-19 synthesis. FGF-19 then binds to the FGFR-4 and klotho β receptors to decrease C4 and subsequent hepatic bile acid synthesis. Right panel: In bile acid malabsorption, bile acids are reabsorbed, but FGF-19 remains low, or there are mutations within the FGFR-4 or klotho β receptors that do not inhibit hepatic bile acid synthesis. Bile acids that enter the colon bind to the GPBAR1 receptor and cause increased colonic transit and secretion. IBS=irritable bowel syndrome.

Reproduced with permission from ref. 34, Camilleri M. Physiological underpinnings of irritable bowel syndrome: neurohormonal mechanisms. J Physiol 2014;592:2967–80.