Chapter 7 - Gastrointestinal hormones

Abstract

The oral cavity, stomach, intestine, colon, liver, gallbladder, and pancreas operate as an integrated physiological unit to effect the digestion and absorption of dietary-acquired nutrients. This chapter focuses on the gastrointestinal (GI) hormones. There are ~30 peptides known to be expressed within the digestive tract, thus making the stomach, intestine, and colon the largest endocrine organ in the body. The regulatory peptides synthesized by the gut include hormones, growth factors, and peptide neurotransmitters. The GI hormones are a family of polypeptides produced by specialized endocrine cells present in the stomach, intestine, and colon which function both as traditional hormonal messengers and as neurotransmitters. These hormones mediate a wide variety of specific biological responses carried out by the stomach, intestine, and colon, as well as the endocrine and exocrine pancreas, liver, and gallbladder, which, when collectively integrated, optimize the physiological conditions necessary to permit the efficient digestion and absorption of protein, carbohydrates, and fat as well as minerals and vitamins from the lumen of the intestine. There is also increasing evidence of neuroendocrine communication between the brain and gut that provides an additional level of integration and complexity to these digestive processes.