Dr John Ingram is a senior research scientist with Plant & Food Research, Auckland. John explains the meaning of the term ‘hormone’ and then describes the function of several digestive tract hormones. Some of these hormones play a key role in signalling to the satiety centres in the brain.
Dr John Ingram
Hormones are chemical messengers involved in communication between cells in the body. They work at incredibly low concentrations. In your average male, for instance, you only have 50 micrograms of testosterone circulating round the body and yet you have such dramatic effects.
There are a variety of hormones released at different levels of the GI tract in response to food. In the stomachgastrin has an effect on the production of gastric juices such as hydrochloric acid and various enzymes. Further down in the duodenum, you will get the release of the hormone called cholecystokinin or CCK, and that has an effect on gastric emptying and also satiety, which is what we’re interested in. Satiety is the absence of hunger or the lack of desire to eat.
The ileum is part of the small intestine, it’s furtherest from the stomach. The ileal brake mechanism is triggered when the ileum sees more nutrients than it normally would. The ileum, in the presence of elevated levels of carbohydrate or lipid, the release of hormones such as GLP-1 and PYY, and again, they’re also involved in gastric function and satiety. These hormones play a key role in signalling to the satiety centres in the brain.