Approximately 5 percent of the total pancreatic mass is comprised of endocrine cells. These endocrine cells are clustered in groups within the pancreas which look like little islands of cells when examined under a microscope. This appearance led to these groups of pancreatic endocrine cells being called “Pancreatic Islets”. Within pancreatic islets are cells which make specific pancreatic endocrine hormones, of which there are only a few (the most famous of course being insulin).
These cells within the islets are called “Pancreatic Islet Cells”.
Pancreatic islets are scattered throughout the pancreas. Like all endocrine glands, they secrete their hormones into the bloodstream and not into tubes or ducts like the digestive pancreas. Because of this need to secrete their hormones into the blood stream, pancreatic islets are surrounded by small blood vessels.
This relationship is shown in the picture of a pancreatic islet where islet cells are secreting their hormones into nearby blood vessels. Remember, the purpose of endocrine cells is to make hormones which are secreted into the blood stream where they gain access to other cells very far away with the goal of making those cells respond in a specific fashion.
Tumours can develop in the Pancreatic Endocine cells and they may produce symptoms because of their over-production of hormones.
Multiple endocrine neoplasia type 1 (MEN 1) is a relatively uncommon inherited disease. Individuals who inherit the gene for MEN 1 have an increased chance of developing overactivity and enlargement of certain endocrine glands. The endocrine glands most commonly affected by MEN 1 are the parathyroid, pancreas, and pituitary glands. Almost everyone who inherits MEN 1 develops overactivity of the parathyroid glands at some stage in their life. The other endocrine glands become overactive less frequently, however, people who inherit MEN 1 will usually develop overactivity in more than one endocrine gland. Overactivity in different endocrine glands may occur simultaneously or at separate times during a persons life.
MEN 1 is a rare condition. On average, fewer than 1 person in every 20,000 will carry the gene for MEN 1. MEN 1 is passed down in families from one generation to the next. MEN 1 can be inherited by a child if one of their parents has MEN 1. Males and females are equally likely to inherit the MEN 1 gene from an affected parent. MEN 1 is known to occur in all major racial groups.
MEN 1 can lead to overactivity and enlargement of the three endocrine glands listed above (the endocrine glands which start with the letter “P”). The different endocrine glands in the body each produce different and specific hormones. Hormones are chemicals which are produced by endocrine glands to regulate the function of various tissues throughout the body. The endocrine glands are relatively small in size and release a controlled amount of their hormone directly into the blood stream. Once in the blood stream, hormones circulate throughout the body. Only small quantities of hormones are needed to produce the required effect throughout the body (a little bit goes a long way!). Under normal circumstances, the level of endocrine gland activity is carefully regulated.
People who inherit the gene for MEN 1 are predisposed to developing an overactivity in hormone production from the parathyroid glands, pituitary gland and pancreas (thetas why physicians will measure hormones in the blood to check for overproduction of each specific hormone). Increased hormone production is usually associated with enlargement of these glands. Endocrine gland enlargement and hormone overproduction does not usually occur in all areas of an endocrine gland at the same point in time. Some parts of overactive endocrine glands grow more rapidly than others, and produce more hormone than other parts of the same gland. The parts of an endocrine gland which grow most rapidly become “lumpy”. These lumps are usually benign. Benign lumps in endocrine glands are known as adenomas.
The surgey for Pancreatic Endocrine Tumours is often complex and requires careful preoperative investigations which are often difficult to interpret. Sometimes only a small amount of tissue needs to be removed (Insulinoma) and sometimes more of the pancreas needs to be resected. In some instances surgery is not indicated.