Pancreatic hormones and their functions in the body
The content of the article:
- Endocrine pancreas
-
What hormones does the pancreas produce?
- Insulin
- Glucagon
- Somatostatin
- Gastrin
- Ghrelin
- Pancreatic polypeptide
- Conclusion
- Video
The pancreas is an important part of the human digestive system. It is the main supplier of enzymes, without which complete digestion of proteins, fats and carbohydrates is impossible. But its activity is not limited to the release of pancreatic juice. The special structures of the gland are the islets of Langerhans, which perform an endocrine function by secreting insulin, glucagon, somatostatin, pancreatic polypeptide, gastrin and ghrelin. Pancreatic hormones are involved in all types of metabolism, a violation of their production leads to the development of serious diseases.
Pancreatic hormones regulate the functions of the digestive system and metabolism
Endocrine pancreas
The cells in the pancreas that synthesize hormone-active substances are called insulocytes. They are located in the iron in clusters - islets of Langerhans. The total mass of the islets is only 2% of the organ weight. By structure, several types of insulocytes are distinguished: alpha, beta, delta, PP and epsilon. Each type of cell is capable of producing and secreting a certain type of hormones.
What hormones does the pancreas produce?
The list of pancreatic hormones is extensive. Some are described in great detail, while the properties of others are still insufficiently studied. The former includes insulin, which is considered the most studied hormone. Representatives of biologically active substances that have not been studied enough include pancreatic polypeptide.
Insulin
Special cells (beta cells) of the islets of Langerhans in the pancreas synthesize a peptide hormone called insulin. The spectrum of action of insulin is wide, but its main purpose is to lower the level of glucose in the blood plasma. The effect on carbohydrate metabolism is realized due to the ability of insulin:
- facilitate the entry of glucose into the cell by increasing membrane permeability;
- stimulate the absorption of glucose by cells;
- activate the formation of glycogen in the liver and muscle tissue, which is the main form of glucose storage;
- suppress the process of glycogenolysis - the breakdown of glycogen to glucose;
- inhibit gluconeogenesis - the synthesis of glucose from proteins and fats.
But not only the metabolism of carbohydrates is the area of application of the hormone. Insulin is able to influence protein and fat metabolism through:
- stimulation of the synthesis of triglycerides and fatty acids;
- facilitating the flow of glucose into adipocytes (fat cells);
- activation of lipogenesis - synthesis of fats from glucose;
- inhibition of lipolysis - the breakdown of fats;
- inhibition of protein breakdown processes;
- increasing the permeability of cell membranes for amino acids;
- stimulation of protein synthesis.
Insulin provides tissues with potential energy sources. Its anabolic effect leads to an increase in the storage of protein and lipids in the cell and determines the role in the regulation of growth and development processes. In addition, insulin affects water-salt metabolism: it facilitates the flow of potassium into the liver and muscles, and helps to retain water in the body.
The main stimulus for the formation and secretion of insulin is an increase in serum glucose levels. Hormones also lead to an increase in insulin synthesis:
- cholecystokinin;
- glucagon;
- glucose-dependent insulinotropic polypeptide;
- estrogens;
- corticotropin.
The defeat of beta cells leads to a lack or absence of insulin - type 1 diabetes develops. In addition to genetic predisposition, viral infections, stress effects, nutritional errors play a role in the occurrence of this form of the disease. Insulin resistance (tissue insensitivity to the hormone) is at the heart of type 2 diabetes.
Insulin production depends mainly on blood glucose levels
Glucagon
The peptide produced by the alpha cells of the islets of the pancreas is called glucagon. Its effect on the human body is opposite to that of insulin and is to increase blood sugar levels. The main goal of maintaining a stable plasma glucose level between meals is accomplished by:
- breakdown of glycogen in the liver to glucose;
- synthesis of glucose from proteins and fats;
- inhibition of glucose oxidation processes;
- stimulation of fat breakdown;
- formation of ketone bodies from fatty acids in liver cells.
Glucagon increases the contractility of the heart muscle without affecting its excitability. The result is an increase in pressure, strength and heart rate. In stressful situations and during physical exertion, glucagon makes it easier for skeletal muscles to access energy reserves and improves their blood supply by increasing the work of the heart.
Glucagon stimulates the release of insulin. With insulin deficiency, the glucagon content is always increased.
Somatostatin
The peptide hormone somatostatin, produced by the delta cells of the islets of Langerhans, exists in two biologically active forms. It inhibits the synthesis of many hormones, neurotransmitters and peptides.
| Scope of influence | Hormone, peptide, enzyme whose synthesis is reduced |
| Hypothalamus | Growth hormone releasing hormone |
| Anterior pituitary gland | Growth hormone, thyrotropin |
| Gastrointestinal tract | Gastrin, secretin, pepsin, cholecystokinin, serotonin |
| Pancreas | Insulin, glucagon, vasoactive intestinal peptide, pancreatic polypeptide, bicarbonates |
| Liver | Insulin-like growth factor 1 |
| Kidney | Renin |
Somatostatin, in addition, slows down the absorption of glucose in the intestine, reduces the secretion of hydrochloric acid, gastric motility and bile secretion. The synthesis of somatostatin increases at high concentrations of glucose, amino acids and fatty acids in the blood.
Gastrin
Gastrin is a peptide hormone, except for the pancreas, produced by cells of the gastric mucosa. By the number of amino acids that make up it, several forms of gastrin are distinguished: gastrin-14, gastrin-17, gastrin-34. The pancreas secretes mainly the latter. Gastrin participates in the gastric phase of digestion and creates conditions for the subsequent intestinal phase by:
- increased secretion of hydrochloric acid;
- stimulation of the production of a proteolytic enzyme - pepsin;
- activation of the release of bicarbonates and mucus by the inner lining of the stomach;
- increased motility of the stomach and intestines;
- stimulation of the secretion of intestinal, pancreatic hormones and enzymes;
- enhancing blood supply and activating the restoration of the gastric mucosa.
Stimulates the production of gastrin, which is influenced by gastric distension during food intake, protein digestion products, alcohol, coffee, gastrin-releasing peptide secreted by nerve processes in the stomach wall. The level of gastrin increases with Zollinger-Ellison syndrome (tumor of the islet apparatus of the pancreas), stress, and the use of non-steroidal anti-inflammatory drugs.
Ghrelin
Ghrelin is produced by epsilon cells of the pancreas and special cells of the gastric mucosa. The hormone makes you feel hungry. It interacts with the centers of the brain to stimulate the secretion of neuropeptide Y, which is responsible for stimulating appetite. The concentration of ghrelin increases before meals and decreases afterwards. The functions of ghrelin are varied:
- stimulates the secretion of growth hormone - growth hormone;
- enhances the secretion of saliva and prepares the digestive system for eating;
- enhances gastric contractility;
- regulates the secretory activity of the pancreas;
- increases the level of glucose, lipids and cholesterol in the blood;
- regulates body weight;
- exacerbates sensitivity to food odors.
Ghrelin coordinates the body's energy needs and participates in the regulation of the state of the psyche: depressive and stressful situations increase appetite. In addition, it has an effect on memory, learning ability, sleep and wakefulness processes. Ghrelin levels increase with fasting, weight loss, low calorie foods, and a decrease in blood glucose. With obesity, type 2 diabetes mellitus, there is a decrease in the concentration of ghrelin.
Ghrelin is a hormone responsible for hunger
Pancreatic polypeptide
Pancreatic polypeptide is a product of pancreatic PP-cell synthesis. It is referred to as food regimen regulators. The effect of pancreatic polypeptide on digestion processes is as follows:
- inhibits the exocrine activity of the pancreas;
- reduces the production of pancreatic enzymes;
- weakens the peristalsis of the gallbladder;
- inhibits gluconeogenesis in the liver;
- enhances the proliferation of the mucous membrane of the small intestine.
The secretion of pancreatic polypeptide is facilitated by protein-rich food, fasting, physical activity, a sharp drop in blood sugar levels. Reduce the amount of somatostatin polypeptide and intravenous glucose released.
Conclusion
The normal functioning of the body requires the coordinated work of all endocrine organs. Congenital and acquired diseases of the pancreas lead to impaired secretion of pancreatic hormones. Understanding their role in the neurohumoral regulation system helps to successfully solve diagnostic and therapeutic problems.
Video
We offer for viewing a video on the topic of the article.
Anna Kozlova Medical journalist About the author
Education: Rostov State Medical University, specialty "General Medicine".
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