The gut is a major producer of hormones, with more than 20 known hormones being responsible for controlling food intake, digestion of food, energy expenditure and influence the pleasure of eating. Some of these digestive hormones target the brain and work in association with the enteric nervous system and is often why the gut is known as the “2nd brain”.
Some of the well known hormones are below:
Gastrin
Gastrin is a hormone that is produced in the lining of the stomach and upper small intestine and is released into the bloodstream. During a meal, gastrin stimulates the stomach to release hydrochloric acid, which then allows the stomach to break down food and absorb certain vitamins such as vitamin B12. Gastric acid also acts as a disinfectant. Gastrin can stimulate the gallbladder to empty its store of bile and the pancreas to secrete enzymes. Gastrin also stimulates growth of the stomach lining and increases the muscle contractions of the gut to aid digestion. (1)
Ghrelin
Ghrelin is a hormone that is produced and released mainly by the stomach with small amounts also released by the small intestine, pancreas and brain. It is known as the ‘hunger hormone’ because it stimulates appetite, increases food intake and promotes fat storage. Ghrelin levels are actually higher in people with lean body weight compared to those who are overweight. High levels of Ghrelin have also been found in people with certain cancers, anorexia nervosa and cachexia. (2)
Glucagon
Glucagon is made by the pancreas and helps regulate your blood glucose (sugar) levels. Glucagon increases your blood sugar level and prevents it from dropping too low, whereas insulin, another hormone, decreases blood sugar levels.
Insulin
Insulin is released from the Pancreas and is essential for helping your body use glucose for energy. If your body cannot produce enough insulin, or your body cannot use the insulin being released, it causes high blood sugar levels. In most people insulin lowers blood sugar levels, stimulates metabolism of glucose, protein, and fat. The inability to produce insulin by destruction of beta cells in the pancreas, creates an autoimmune condition which results in Type 1 Diabetes Mellitus and those diagnosed require injections of insulin for the rest of their lives. Type 2 Diabetes Mellitus is when the body cannot properly use insulin, and is often a result of poor eating and lifestyle habits which results in insulin resistance. (3) (4)
Insulin-like growth factor (IGF-1)
IGF is a hormone that your body makes naturally in the liver and acts much like insulin. It used to be known as somatomedin. IGF helps to control growth hormone secretion in the pituitary gland. IGF works with growth hormones to promote growth and development of bone and tissue. These hormones also affect how your body metabolizes sugar, or glucose. IGF and insulin can work together to rapidly reduce the level of glucose in your blood.
Leptin
Leptin is a hormone released by body fat that helps your body maintain normal weight on a long-term basis. It does this by regulating hunger by providing the sensation of satiety (feeling full). As leptin is created by stored body fat, the higher level of body fat means a higher release of leptin. This signal should mean that the person stops eating. For those on weight loss protocols, as your body fat decreases, your leptin levels decrease, which may signal your body to think that it is suddenly in starvation, which it clearly is not. This feeling of starvation can stimulate hunger and appetite and can lead to increased food consumption. (5)
Gastric Inhibitory Peptide (GIP)
GIP is a member of the secretin family of hormones. It was discovered in extracts of intestine that inhibited gastric motility and secretion of acid, and initially called enterogastrone. It is secreted from mucosal epithelial cells in the first part of the small intestine.
GIP enhances the release of insulin in response to infusions of glucose. For this action, it has also been referred to as glucose-dependent insulinotropic peptide.
Secretin
Secretin is a digestive hormone secreted by the wall of the upper part of the small intestine (the duodenum) that regulates gastric acid secretion and pH levels in the duodenum. When hydrochloric acid passes from the stomach into the duodenum, secretin is released into the bloodstream and stimulates the duct cells of the pancreas to secrete water and bicarbonate. By this mechanism, hydrochloric acid secreted by the stomach is diluted and neutralized. Secretin also inhibits the secretion of gastrin, which triggers the initial release of hydrochloric acid into the stomach, and delays gastric emptying. (6)
References
- Gastrin | You and Your Hormones from the Society for Endocrinology. (n.d.). https://www.yourhormones.info/hormones/gastrin/
- Ghrelin | You and Your Hormones from the Society for Endocrinology. (n.d.). https://www.yourhormones.info/hormones/ghrelin/
- (2023, December 6). Type 1 diabetes | Diabetes Australia | Diabetes Australia. Diabetes Australia. https://www.diabetesaustralia.com.au/about-diabetes/type-1-diabetes/
- Healthdirect Australia. (2021, November 4). Type 2 diabetes. https://www.healthdirect.gov.au/type-2-diabetes
- Professional, C. C. M. (n.d.-d). Leptin & Leptin Resistance. Cleveland Clinic. https://my.clevelandclinic.org/health/articles/22446-leptin
- Utiger, R. D. (1998, July 20). Secretin | Definition & Function. Encyclopedia Britannica. https://www.britannica.com/science/secretin
