Intestinal Hormones – Functions, Importance and Disorders
Intestinal hormones are signaling molecules produced in the digestive tract that regulate digestion, metabolism, and hunger. They form the largest hormonal system in the body.
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Intestinal hormones are signaling molecules produced in the digestive tract that regulate digestion, metabolism, and hunger. They form the largest hormonal system in the body.
What Are Intestinal Hormones?
Intestinal hormones – also known as gastrointestinal hormones or gut hormones – are chemical messenger substances produced by specialized cells lining the gastrointestinal tract and released into the bloodstream. They belong to the enteroendocrine system, which is the largest hormone-producing system in the human body. Intestinal hormones regulate a wide range of vital processes, including digestion, nutrient absorption, appetite control, and metabolic function.
Key Intestinal Hormones and Their Functions
Gastrin
Gastrin is produced mainly in the stomach (G-cells of the gastric antrum) and stimulates the secretion of gastric acid. It plays a central role in protein digestion and gastric motility.
Secretin
Secretin is released in the small intestine when acidic stomach contents enter the duodenum. It stimulates the pancreas to release bicarbonate, which neutralizes stomach acid, and inhibits gastric acid production at the same time.
Cholecystokinin (CCK)
Cholecystokinin is produced in the upper small intestine and promotes the release of digestive enzymes from the pancreas as well as the emptying of the gallbladder. It also transmits satiety signals to the brain.
GLP-1 (Glucagon-like Peptide-1)
GLP-1 is secreted after a meal by L-cells in the small and large intestine. It stimulates insulin release from the pancreas, inhibits glucagon secretion, slows gastric emptying, and reduces appetite. GLP-1 is of major medical importance in the treatment of type 2 diabetes and obesity.
GIP (Glucose-dependent Insulinotropic Peptide)
GIP is released in the small intestine after food intake and – similarly to GLP-1 – supports insulin secretion. Both hormones are collectively referred to as incretins.
Peptide YY (PYY)
Peptide YY is secreted after eating by L-cells in the ileum and colon. It slows intestinal transit and reduces hunger by acting on the brain.
Ghrelin
Ghrelin is produced mainly in the stomach and is the only known hunger-stimulating gut hormone. Its levels rise before meals and fall after eating. It plays an important role in body weight regulation.
Motilin
Motilin is produced in the small intestine and regulates the rhythmic contractions of the gastrointestinal tract between meals, known as the migrating motor complex. These movements are important for clearing food residues and preventing bacterial overgrowth.
Vasoactive Intestinal Peptide (VIP)
VIP functions as both a neurotransmitter and a hormone in the gut. It relaxes smooth muscle, promotes fluid secretion into the intestinal lumen, and regulates blood flow in the digestive tract.
Relevance to Health and Disease
An imbalance in intestinal hormones can lead to or contribute to various medical conditions, including:
- Type 2 diabetes mellitus: Impaired GLP-1 signaling and disrupted insulin secretion.
- Obesity: Alterations in ghrelin, PYY, and GLP-1 affect hunger and satiety.
- Irritable bowel syndrome: Changes in serotonin release and other gut signaling molecules.
- Zollinger-Ellison syndrome: Excessive gastrin production by a tumor (gastrinoma).
- VIPoma: A tumor that overproduces VIP, causing severe, watery diarrhea.
Therapeutic Use of Intestinal Hormones
Intestinal hormones have become highly relevant in modern medicine. In particular, GLP-1 receptor agonists – synthetic compounds that mimic the action of GLP-1 – are successfully used to treat type 2 diabetes and to support weight loss in obesity. Well-known agents in this class include semaglutide and liraglutide.
DPP-4 inhibitors (gliptins) also work via the incretin system by slowing the breakdown of GLP-1 and GIP, thereby prolonging their blood sugar-lowering effects.
Intestinal Hormones and the Microbiome
Emerging research shows that the gut microbiome – the community of microorganisms living in the intestine – influences the production and release of intestinal hormones. Short-chain fatty acids produced by gut bacteria, for example, stimulate the secretion of GLP-1 and PYY. This highlights the close connection between gut health, the hormonal system, and metabolism.
References
- Rehfeld, J. F. (2014): A centenary of gastrointestinal endocrinology. In: Hormone and Metabolic Research, 46(11), 764-771. DOI: 10.1055/s-0034-1390466
- Drucker, D. J. (2006): The biology of incretin hormones. In: Cell Metabolism, 3(3), 153-165. DOI: 10.1016/j.cmet.2006.01.004
- World Gastroenterology Organisation (WGO): Guidelines on gut microbiota and intestinal hormones. Available at: www.worldgastroenterology.org
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Related search terms: Intestinal Hormones + Gut Hormones + Gastrointestinal Hormones + Enteric Hormones