The pancreas is a dual-functional gland with both exocrine (digestive) and endocrine (hormonal) functions.
In this article, we shall look at the endocrine functions of the pancreas and their clinical significance.
Structure of the Pancreas
The pancreas is a partially retroperitoneal, abdominal organ found posterior and inferior to the stomach. Further information on the anatomy of the pancreas can be found here.
There are a variety of cell groups within the pancreas. Firstly, there are clusters of cells known as Islets of Langerhans. These islets contain the cell types that produce the hormones relating to the endocrine functions of the pancreas. There are also acini and duct systems within the pancreas, which are responsible for producing enzymes relating to the exocrine functions of the pancreas.
Islets are thought to make up 5% of the overall volume of the pancreas, although they receive around 15% of its blood flow. The Islets of Langerhans contain the following cell types:
- Alpha cells – these make up roughly 15-20% of Islet cells and are responsible for producing glucagon
- Beta cells – these make up 65-80% of Islet cells and produce insulin and amylin
- Delta cells – these make up 3-10% of Islet cells and produce somatostatin
- Gamma cells – these make up 3-5% of Islet cells and are responsible for production of pancreatic polypeptide
- Epsilon cells – these make up less than 1% of Islet cells and produce ghrelin
By User:Polarlys (Own work) CC BY 2.5 (http://creativecommons.org/licenses/by/2.5)], via Wikimedia Commons
Fig 1 – The lighter tissue in this section is the Islet cells. The darker staining tissue is pancreatic acini.
Pancreatic Hormones
Pancreatic hormones are produced in the Islets of Langerhans. Scattered throughout exocrine tissue in the tail of the pancreas, these are spherical groups of different cell types producing different polypeptide hormones.
There are 6 key polypeptide hormones secreted by the endocrine pancreas. The table below summarises the cells that produce these and the main functions of these hormones:
| Pancreatic Hormone | Produced by | Function |
| Insulin | Beta cells | Decrease blood glucose levels |
| Amylin | Beta cells | Slows gastric emptying to prevent spikes in blood glucose levels |
| Glucagon | Alpha cells | Increase blood glucose levels |
| Somatostatin | Delta cells | Regulates Islet cell secretion of other hormones |
| Pancreatic Polypeptide | Gamma cells | GI function |
| Ghrelin | Epsilon cells | Increase in appetite |
These hormones can also regulate the action of other cell types within the Islets.
- Insulin stimulates action of beta cells and inhibits alpha cells.
- Glucagon stimulates action of alpha cells, which in turn then leads to activation of beta and delta cells
- Somatostatin leads to inhibition of both alpha and beta cells.
Clinical Relevance – Type 1 Diabetes Mellitus
Diabetes mellitus is an endocrine disorder characterised by chronic hyperglycaemia due to either insulin resistance and/or insulin deficiency. Type 1 diabetes mellitus mainly affects younger people <30 years
There is absolute insulin deficiency due to autoimmune destruction of pancreatic beta cells. This means that the beta cells are recognised as “foreign” or “non-self” by the body and so are attacked and destroyed by the body’s immune system.
Viral infection in a young person with pre-disposing factors, e.g. family history, is a common trigger. In some cases there is relative insulin deficiency due to defective beta cells and inadequate insulin secretion or rate of secretion.
Commonly, type 1 diabetes mellitus presents with a classic triad of symptoms: polyuria, polydipsia and weight loss. Due to the lack of insulin being produced by the body in type 1 diabetes, patients must be treated with injectable insulin regime.
The average age of diagnosis in the UK is between 10 and 14 years, therefore effective patient education forms an important part of treatment for this disease. It is a lifelong disease which needs tight control of glucose levels and explaining the importance to children and young adults can be challenging.
