Hormones Produced by the Pancreas and Islets of Langerhans
The islets of Langerhans are the portion of the pancreas that give it its endocrine functionality. These regions contain 5 types of hormone-producing cells which impart the pancreas with the ability to produce various hormones such as insulin.
The islets of Langerhans make up less than 2% of the pancreas by weight – most of the pancreas is dedicated to digestion rather than hormone production.
There are 5 important cell types that make up the islets of Langerhans: alpha cells, beta cells, delta cells, Epsilon cells, and PP cells. Below, you will discover what hormones each of these cells produces and what the role of each of these hormones is.
Alpha cells are responsible for producing glucagon, a very important hormone. Glucagon takes the opposite role of insulin in that glucagon helps prevent the body’s blood glucose (sugar) level from dropping too low. When glucagon is released, it enters the liver and stimulates the breakdown of glycogen (stored glucose) into glucose and then releases that glucose into the blood stream.
This process occurs when blood glucose falls in order to help maintain steady levels of blood glucose.
Beta cells are the cells responsible for producing insulin and make up the bulk of the islets of Langerhans. Beta cells are destroyed by the immune system in Type-1 diabetes. However, in Type-1 Diabetes, the rest of the pancreas typically remains intact as the immune cells specifically target beta cells. This is why people with Type-1 diabetes need insulin replacement but do not require replacement of digestive enzymes.
Insulin production and release is triggered by events related to food intake, such as rising blood sugar and food in the duodenum. Even the taste of something sweet can stimulate the release of insulin!
Delta cells are responsible for producing somatostatin. Somatostatin is essentially an “off switch” for digestion, reducing the secretion of enzymes and hormones responsible for digestion as well as decreasing the rate at which food leaves the stomach and enters the duodenum for digestion. This is a self-regulator that prevents too many digestive enzymes from being produced.
Epsilon cells are responsible for the production of ghrelin, a peptide hormone responsible for inducing hunger. This helps the pancreas exert a better control over blood sugar. The pancreas will produce ghrelin to make you hungry so that you eat something. This will help provide more glucose to help keep blood sugar stable. After eating, ghrelin levels fall. This process of falling ghrelin is integral to satiety.
PP (pancreatic polypeptide) cells, also called F Cells, are the pancreatic cells which produce amylin. Amylin is the pancreas’ counter-point to ghrelin; Amylin slows gastric emptying and reduces hunger after eating. This is done as blood glucose rises to prevent blood glucose from getting too high right after eating.
An Overview of the Endocrine System and the Islets of Langerhans
Now that you know the function of all 5 cell types and their primary products, you can put them all together to see how the pancreas helps manage blood sugar and hunger:
- When blood glucose levels drop, alpha cells in the pancreas will produce glucagon which frees up stored glucose in the liver. This stored glucose will maintain blood glucose levels until you can eat.
- As blood glucose levels drop, the epsilon cells in the pancreas release ghrelin. Ghrelin makes you hungry and encourages the brain to seek out food so that the body does not have to continue to rely on stored glucose.
- Motivated by ghrelin and a host of other signaling pathways, you seek out food. The taste of food begins the carefully controlled release of insulin, which is produced by beta cells. Insulin release continues as needed until blood glucose levels once again reach normal levels.
- As digestion occurs, the release of digestive enzymes is modulated by somatostatin to ensure things to do not happen too quickly. Somatostatin is produced by delta cells.
- After enough food has been ingested and blood sugar rises, the pancreas finally releases amylin, produced by PP cells, to promote satiety (feeling full) and to slow down gastric emptying to prevent blood glucose from getting too high.