Pancreatic Endocrine Tumours

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

Tumours can develop in the Pancreatic Endocine cells and they may produce symptoms because of their over-production of hormones.

MEN I:

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.

Surgery

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.

Pancreatic Endocrine Hormones and Their Purpose

Insulin

Purpose:     Regulate blood glucose (sugar) in the normal range.

Action:    Forces many cells of the body to absorb and use glucose thereby decreasing blood sugar levels

Secreted in response to:     High blood glucose

Secretion inhibited by:     Low blood glucose

Disease due to deficient action:     Diabetes

Disease due to excess action:     HypoglycemiaTumor called:    Insulinoma.

Glucagon

Purpose:     Assist insulin in regulating blood glucose (sugar) in the normal range

Action:    Forces many cells of the body to release (or produce) glucose (increasing blood sugar)

Secreted in response to:     Low blood glucose

Secretion inhibited by:     High blood glucose

Disease due to deficient action:     Some times nothing, sometimes hypoglycemia (Skin Rash – Migratory Necroltic Erythema)

Disease due to excess action:     Hyperglycemia

Tumor called:    Glucagonoma

Somatostatin

Purpose:     Regulate the production and excretion of other endocrine tumors

Action:    Slows down production of insulin, glucagon, gastrin, and other endocrine tumors

Secreted in response to:     High levels of other endocrine hormones

Secretion inhibited by:     Low levels of other endocrine hormones

Disease due to deficient action:     Poorly defined

Disease due to excess action:     Diabetes (inhibits insulin production), gallstones, and dietary fat intolerance.

Tumor called:     Somatostatinoma

Gastrin

Purpose:     Assist in digestion within the stomach

Action:    Induce acid producing cells of the stomach to produce acid

Secreted in response to:     Food in the stomach and intestines

Secretion inhibited by:     Absence of food in stomach and intestines

Disease due to deficient action:     Poorly defined, some times no symptoms at all

Disease due to excess action:     Stomach ulcers due to excess stomach acid

Tumor called:    Gastrinoma (also called Zollinger Ellison Syndrome)

Vasoactive Intestinal Peptide (VIP)

Purpose:     Help control water secretion and absorption from the intestines

Action:    Causes intestinal sells to secrete water and salts into the intestines (inhibit absorption)

Secreted in response to:     Unclear

Secretion inhibited by:     UnclearDisease due to deficient action:     No symptoms at all

Disease due to excess action:     Severe watery diarrhea and salt (potassium) imbalances

Tumor called:    VIPoma

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