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Role of insulin and other hormones in diabetes

What is glucose?

Our bodies require energy to function properly and we get that energy from three food groups: protein, fat, and carbohydrates (sugars, starches, and fibers). When the body digests carbohydrates, they are transformed through digestion into a very important source of instant energy, a form of sugar called glucose.1,2

Three forms of simple sugars (also called monosaccharides) are able to enter the bloodstream directly after digestion. These are often broken down from more complex sugars (polysaccharides and disaccharides). These simple sugars include glucose (found in most carbohydrates, including grains and starches), fructose (found in fruits and vegetables), and galactose (found in dairy products and in certain vegetables). The word glucose comes from the Greek word for sweet, and it is the key source of energy for cells in the body. Upon digestion, glucose can be used for instant energy or stored in the form of glycogen when the body’s energy needs are being met.1,2

The impact of insulin and other hormones on glucose control

Our bodies depend on the action of a number of different hormones, working together in conjunction, to control how we use glucose.

We depend on insulin, a hormone produced in the beta cells of the pancreas (an organ located behind the stomach) to use glucose. Insulin serves as sort of a “gatekeeper,” allowing glucose to enter cells where it can be transformed into energy and used to support vital cell functions. Insulin also has other important functions related to the way our body uses glucose.3,4

In addition to insulin, another hormone produced by beta cells called amylin controls how quickly glucose is released into the bloodstream after a meal. It does this by slowing the emptying of the stomach and increasing the feeling that your stomach is full.

A group of hormones called incretins (this includes the hormone glucagon-like peptide 1 [GLP-1]) are produced by the intestine and stimulate the body to produce insulin after eating. By enhancing the release of insulin, incretins also slow emptying of the stomach, promote the feeling of fullness, and delay the release of glucose into the bloodstream.

Incretins work to prevent the hormone glucagon from being released by the pancreas. Glucagon, which is made by the alpha cells of the pancreas, is responsible for transforming glycogen stored in the liver and muscles back into glucose to satisfy the body’s energy needs when food isn’t available.4

Type 2 diabetes and loss of glucose control

All of the hormones introduced above normally work together in a balanced fashion to control glucose in the body and supply the body with its energy needs. What happens in type 2 diabetes is that the body loses the ability to use the insulin it produces effectively (this is called “insulin resistance”). In addition to insulin resistance, the body loses the ability to produce insulin. Deficiencies and loss of coordination among the other hormones involved in glucose control also contribute to type 2 diabetes.5

Learn more about the role of the pancreas and other organs and tissues in diabetes

Role of insulin

Key functions of insulin in the body

  • Allows glucose entry into cells
  • Stimulates glucose storage in muscle and liver
  • Regulates blood sugar levels by inhibiting liver glucose production
  • Stimulates growth of fat and muscle

Insulin is one of the true heroes of the body, a kind of super traffic cop. It doesn’t have the flashy job of chasing down criminals (like the officers in the immune system), but it is in charge of making sure energy traffic (in the form of glucose) flows smoothly and arrives at its cellular destinations. To achieve this, insulin combines almost all of the functions of a well constructed traffic system: it goes to specific locations to facilitate the transport of glucose, it monitors the glucose needs of the body and sends signals to organs and tissues to store glucose as needed, it monitors blood glucose and communicates with the liver to control glucose production, and it can even instruct the body to grow fat and muscle tissue as needed.4

Allows glucose entry into cells

Insulin travels from headquarters (the pancreas, where it is produced) via the bloodstream to individual tissues and cells where it unlocks the gates so that glucose can enter and supply energy.

Stimulates glucose storage

If the energy needs of cells are being met, insulin communicates that to muscle and liver cells and stimulates them to store excess glucose in the form of glycogen, which can later be transformed back into glucose and used for energy when the body needs it.

Regulates blood sugar levels

Insulin also has a key role in regulating blood sugar. If it detects that there is excess glucose in the bloodstream, it can stimulate the liver to stop the chemical reactions that produce glucose.

Stimulates the growth of fat and muscle

Not only does insulin help conduct the flow of glucose traffic, it also knows when there is a need for fat and muscle and as a “builder hormone” stimulates the growth of these tissues.

Written by: Jonathan Simmons | Last reviewed: May 2014.
  1. Diabetes Overview. National Diabetes Information Clearinghouse (NDIC). Available at: http://diabetes.niddk.nih.gov/dm/pubs/insulinresistance/#what. Accessed 12/04/13.
  2. Dods RF. Understanding Diabetes: A Biochemical Perspective. Hoboken, NJ: Wiley; 2013.
  3. Insulin Resistance and Prediabetes. National Diabetes Information Clearinghouse (NDIC). Available at: http://diabetes.niddk.nih.gov/dm/pubs/insulinresistance/#what. Accessed 12/04/13.
  4. Mantzoros C, Serdy S. Insulin action. Nathan DM, Mulder JE, eds. UptoDate. Wolters Kluwer Health. Accessed at: www.uptodate.com. 2013.
  5. Defronzo RA. Banting Lecture. From the triumvirate to the ominous octet: a new paradigm for the treatment of type 2 diabetes mellitus: Diabetes. 2009 Apr;58(4):773-95.