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Glucagon, Hypoglycemia, and Diabetes: Control of Blood Sugar

Linda Crampton is a writer and teacher with a first-class honors degree in biology. She often writes about the scientific basis of disease.

The pancreas is nestled into the curve formed by the duodenum, which Is the first part of the small intestine. It makes both glucagon and insulin.

The pancreas is nestled into the curve formed by the duodenum, which Is the first part of the small intestine. It makes both glucagon and insulin.

What Is Glucagon?

Many people have heard of insulin, a hormone made by the pancreas that lowers the blood sugar level and that people with type 1 diabetes lack. There is another pancreatic hormone that also has an important effect on blood sugar, however. This hormone is glucagon. Glucagon has the opposite effect to insulin. It raises the blood sugar level instead of lowering it.

Glucose (blood sugar) is obtained from the food that we digest. The glucose enters our blood through the lining of the small intestine and is used as an energy source by our cells. The concentration of glucose in the blood is affected by the frequency of eating, the amount and types of food that we eat, the amount of exercise that we perform, the use of certain medications, and other factors.

Insulin and glucagon work to keep the glucose level in the blood constant, which is very important for the functioning of the brain. The brain requires a continuous supply of glucose. A glucose level that is too low or too high can both be dangerous. A very low blood sugar level will have an immediate effect on the brain while the effects of continually high blood sugar generally take longer to develop, however.

The pancreas is an unusual organ. It has two completely different functions. The islet cells secrete hormones while the acinar cells secrete digestive enzymes.

The pancreas is an unusual organ. It has two completely different functions. The islet cells secrete hormones while the acinar cells secrete digestive enzymes.

The Pancreas and the Liver

The pancreas and the liver both affect blood sugar, but they do this by different methods. The pancreas releases hormones that control the blood sugar level. The liver affects the blood sugar level by storing and releasing glucose as required.

Glucagon and the Pancreas

Glucagon and insulin are made in a part of the pancreas called the islets of Langerhans or the pancreatic islets. Glucagon is made by the alpha cells in the islets while insulin is made by the beta cells. The hormones are released into the bloodstream when necessary. They bind to cell membranes and cause specific effects, which are described later in this article.

Glycogen and the Liver

In the liver, glucose molecules are joined together to make a molecule called glycogen. Glycogen acts as a storage reservoir for glucose molecules. The liver absorbs glucose and makes glycogen when the glucose level in the blood is too high. It breaks glycogen down and releases glucose into the bloodstream when the blood glucose concentration is too low. The liver is also able to make glucose molecules from amino acids.

Glucagon and glycogen are sometimes confused due to the similarities in their names. Glucagon is a peptide hormone made by the pancreas. Glycogen is a carbohydrate made by the liver.

Hormones and their Action

Like insulin, glucagon is a peptide hormone and is made of amino acids. A glucagon molecule is a chain of twenty-nine amino acids. Hormones are chemical messengers that travel from their site of origin to their target organ through the blood. When they reach the target, they bind to receptors on the surface of cells. Receptors are proteins on or in the cell membrane that cause a specific effect when they join to the correct molecule.

Insulin, Glucagon, and Blood Sugar Control

As the blood glucose concentration rises and falls during our body's activities, insulin and glucagon act to keep the glucose level constant.

  • When the level in the blood is too high, insulin is released from the pancreas and binds to receptors on cell membranes. This process triggers the passage of glucose into the cells, including those of the liver. Excess glucose is stored in the liver as glycogen.
  • When the blood sugar level is too low, glucagon is released from the pancreas. It binds to liver cells and stimulates the liver to produce glucose by two methods: glycogenolysis and gluconeogenesis.

Glycogenolysis

When glucagon joins to its receptors on liver cell membranes, enzymes that break down glycogen are activated. As the glycogen breaks down, glucose molecules are released. The glucose molecules are then transported into the blood, raising the blood sugar level. The breakdown of glycogen is called glycogenolysis. The term may be easier to remember if a person realizes that in biology "lysis" means the breaking down of a structure or substance.

Gluconeogenesis

Glucagon has another important effect on the liver, which also raises the blood sugar level. It stimulates the conversion of amino acids to glucose, a process known as gluconeogenesis. "Genesis" means creation and "neo" means new. The term gluconeogenesis refers to the creation of new glucose molecules.

Comparison of Glucagon and Insulin

HormoneOrigin FunctionNotes

Glucagon

Alpha cells of pancreatic islets

Raises blood sugar

Triggers glyogenolysis and gluconeogenesis

Insulin

Beta cells of pancreatic islets

Lowers blood sugar

Triggers the entry of glucose into cells

Hormones and Blood Sugar Level

Hypoglycemia in Type 1 Diabetics

Type 1 diabetes is a disorder in which the pancreas no longer makes insulin or makes only a tiny amount. It's an autoimmune condition. The patient's immune system mistakenly attacks and destroys the beta cells in the pancreas. The disorder is generally treated with insulin injections. The timing and quantity of insulin that is injected is vitally important. Too little or too much insulin in the bloodstream in relation to blood sugar level can both be dangerous.

Hypoglycemia is an abnormally low level of blood sugar. The decrease is much larger than the moderate decrease that develops when we haven't eaten for a while or when we've exercised, which glucagon compensates for. In hypoglycemia, the blood sugar may be dangerously low, which can prevent the brain from working properly.

People with type 1 diabetes are in danger of developing hypoglycemia. The condition may occur if the person takes too much insulin, exercises harder than normal, hasn't eaten enough, has drunk too much alcohol, or has taken certain medications which have the side effect of lowering blood sugar.

When people with diabetes develop hypoglycemia, their body may not be able to produce enough glucagon to compensate for the lowered glucose level, or it may not be able to produce glucagon fast enough. First aid and/or medical treatment may be necessary.

Most diabetics have a glucose meter or another method of measuring their blood sugar level. This helps to prevent a problem from developing when their glucose level falls or rises.

Possible Symptoms of Hypoglycemia

Some possible symptoms of hypoglycemia are listed below. Not all of the symptoms in the list may be experienced by someone with the condition. In addition, a patient may experience symptoms that aren't on the list or the symptoms that do exist may signify the presence of a different disorder.

The symptoms may include:

  • trembling
  • sweating
  • blurred vision
  • tiredness
  • confusion
  • pale skin
  • headache
  • rapid or pounding heartbeat
  • hunger
  • feeling faint

Someone suffering from hypoglycemia may also have altered behavior, including aggression. In severe cases they may experience seizures or a coma.

Anyone who is experiencing unexplained, unusual, or severe symptoms of a health problem should visit a doctor for a diagnosis and treatment recommendations.

Severe Diabetic Hypoglycemia

Possible Treatments

Mild hypoglycemia in diabetics may be treated by giving the person sweet substances to eat or drink, such as glucose tablets, sugar, honey, or fruit juices. This treatment may be followed by giving the person more substantial food, such as milk, crackers, or a peanut butter sandwich. The person's condition must be monitored after the treatment. If their condition doesn't improve, they need medical help.

Severe hypoglycemia is life threatening and must be treated by a doctor. In the severe version of the condition, the person loses consciousness or is barely conscious. They are also unable to swallow. A common treatment for severe hypoglycemia is a glucagon injection. Some diabetics have their own glucagon injector, which they carry around with them. Schools may keep a glucagon injector on their premises. Even if a helper injects a severely hypoglycemia diabetic with glucagon and the injection appears to eliminate the person's symptoms, the patient must see a doctor.

Family and acquaintances of someone with diabetes should be familiar with the symptoms of hypoglycemia and its treatments. If they are expected to give a glucagon injection when necessary, they should know the correct technique for giving the injection. Glucagon is supplied as a powder and must be mixed with sterile water just before injection. If it's mixed too early it will become inactive. The water is provided in the injection kit.

I think the instructions for giving a glucagon injection in the video below are good, but the narrator makes one error in the information that she presents. She says that glucagon is released by the liver when it is actually released by the pancreas.

How to Use a Glucagon Injector

Hypoglycemia in Type 2 Diabetes

In type 1 diabetes, the pancreas produces no or very little insulin. In people with type 2 diabetes, the pancreas does produce insulin. However, the body's cells are often resistant to the hormone's presence and no longer fully respond to it. This prevents sufficient glucose from entering the cells. In some cases, the disorder appears when the pancreas is unable to make enough insulin for the body's needs.

People with type 2 diabetes may be treated with lifestyle changes, medications, and sometimes insulin injections. Patients may sometimes develop mild hypoglycemia and occasionally a severe form of the disorder which requires glucagon administration. People with type 2 diabetes are less likely to require supplemental glucagon than those with type 1 diabetes, however.

There are glucagon receptors in the intestine and other parts of the body as well as in the liver.

There are glucagon receptors in the intestine and other parts of the body as well as in the liver.

Although hypoglycemia is most common in people with diabetes, it sometimes occurs in people without the disease. A doctor must diagnose non-diabetic hypoglycemia, discover the specific cause of the problem, and prescribe treatment. Dietary first aid measures are the same as in hypoglycemia in diabetics. If these measures don't help or if symptoms are severe, the person must visit a doctor immediately.

Current Research

As with other hormones, scientists are finding that glucagon may have more functions and more complex behaviour than they previously thought. There are glucagon receptors on cells in the brain, kidney, intestinal smooth muscle, and adipose (fat) tissue as well as on liver cells.

The instructions for making glucagon are encoded in the GCG gene. Like other genes, the GCG gene contains instructions for making a protein. This protein is called preproglucagon. It's broken down into a smaller protein called proglucagon. This in turn breaks down into even smaller proteins, one of which is glucagon. The functions of the other proteins that are produced is of great interest to researchers.

Another topic of interest for scientists is the control of glucagon production and the role of nervous system secretions. At the moment, the control system is not well understood. Understanding the system could be very important for helping diabetics.

An islet of Langerhans or pancreatic islet (the paler area in this stained slide) makes both glucagon and insulin.

An islet of Langerhans or pancreatic islet (the paler area in this stained slide) makes both glucagon and insulin.

The Nature of Diabetes

Type 1 diabetes was once thought to be simply a pancreatic problem in which insulin is no longer produced by the pancreatic islets. According to this theory, if the insulin is replaced, the person's symptoms will disappear.

A lack of insulin is certainly involved in type 1 diabetes and insulin is definitely an essential treatment for the disorder. However, researchers suspect that the interactions between the central nervous system, insulin, glucagon, and perhaps hormones that resemble glucagon are also important in diabetes. Understanding these interactions may lead to new treatments for the disease.

The human endocrine system, or the hormonal system, is very complex. There's still a lot to be learned about hormone identity, secretion, and action. Researchers are gradually discovering how hormones such as glucagon work, however, which could be very helpful for treating disease.

References

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2012 Linda Crampton

Comments

Linda Crampton (author) from British Columbia, Canada on November 02, 2013:

Thanks, tirelesstraveler. I appreciate your visit and comment!

Judy Specht from California on November 02, 2013:

Your writing is easy to follow and engaging even when the topics are complex. The pictures of the pancreas are amazing.

Linda Crampton (author) from British Columbia, Canada on July 28, 2012:

I am so sorry that you lost your father from diabetes complications, Pollyannalana. Thank you for sharing the dietary information - anything that can help diabetics is very useful, especially when it's a healthy food like lentils or barley.

Pollyannalana from US on July 28, 2012:

My dad died from complications linked to diabetes. I gave him his shots for years. There are foods that can help fight sugar like lentils and barley for example. I think anything we can find in the natural could be what will save our lives and maybe not die the horrible death my dad did.

Linda Crampton (author) from British Columbia, Canada on July 28, 2012:

Thanks, Prasetio. I appreciate your visit, the comment and the votes!

prasetio30 from malang-indonesia on July 28, 2012:

Very informative hub. Again...I learn many things from this hub. Voted up and useful. Take care :-)

Prasetio

Linda Crampton (author) from British Columbia, Canada on July 27, 2012:

Hi, drbj. Thank you very much for the comment. Insulin is certainly a very important hormone, but people often forget - or don't realize - that glucagon is insulin's partner, and that both hormones are needed to keep the blood sugar level constant!

drbj and sherry from south Florida on July 27, 2012:

As you point out in this excellent article, Alicia, insulin is much more well known to the general public than the other pancreatic hormone, glucagon. Guess the former elicits more PR than the latter.

Linda Crampton (author) from British Columbia, Canada on July 27, 2012:

Hi, Tom. Thank you for voting and for the comment! I hope that your weekend is wonderful too.

Thomas Silvia from Massachusetts on July 27, 2012:

Hi my friend, very interesting and useful information for those who may have had some of these symptoms of hypoglycemia .

Well done and vote up and more !!!

Have a awesome weekend my friend ! :-)

Linda Crampton (author) from British Columbia, Canada on July 26, 2012:

Thank you very much, editorsupremo. Yes, insulin is much better known by most people. The fact that glucagon also plays a role in controlling blood sugar is sometimes a surprise for people!

editorsupremo from London, England on July 26, 2012:

Excellent and informative hub. Insulin is the hormone that everybody knows is related to diabetes but very little is mentioned or known about glucagon. Thanks for reporting on this other hormone that can have a serious effect on blood glucose levels.

Linda Crampton (author) from British Columbia, Canada on July 26, 2012:

Thanks, mperrottet. It's nice to meet you! I have a friend who is a diabetic, but no one in my family has the disorder.

Margaret Perrottet from San Antonio, FL on July 26, 2012:

Very informative article. My husband is diabetic, so I'm always interested in things related to diabetes.

Linda Crampton (author) from British Columbia, Canada on July 26, 2012:

Thank you very much for the kind comment, GoodLady!! I appreciate your visit.

Penelope Hart from Rome, Italy on July 26, 2012:

You did succeeded in making the topic understandable. I was fascinated throughout, very, very interesting.

Linda Crampton (author) from British Columbia, Canada on July 26, 2012:

Thank you for the visit and comment, Bill! I appreciate your comment very much, because my goal was to make the topic easy to understand for someone who doesn't have a science background.

Bill Holland from Olympia, WA on July 26, 2012:

Really very informative and educational. I like the way you can write about something very technical and make it easy to understand. Well done my friend.