The Important Role of Insulin and Glucagon in Maintaining Homeostasis

The human body requires that the blood glucose level is maintained in a very narrow range.  Homeostasis is regulated by two hormones, insulin and glucagon which are both secreted by the endocrine pancreas.  The production of insulin and glucagon by these pancreatic cells ultimately determines if a patient has diabetes or another related problem [4].

Source: and glucagon regulate blood sugar.


Insulin is secreted by the beta cells of the pancreas in response to high blood sugar, although a low level of insulin is always secreted by the pancreas.  After a meal, the amount of insulin secreted into the blood increases as the blood glucose rises.  Likewise, as blood glucose falls, insulin secretion by the pancreatic islet beta cells decreases.

In response to insulin, cells (muscle, red blood cells, and fat cells) take glucose in from the blood, which ultimately lowers the high blood glucose levels back to the normal range [4].


Glucagon is secreted by the alpha cells of the pancreas when blood glucose is low.   Blood glucose is low between meals and during exercise.  When blood glucose is high, no glucagon is secreted from the alpha cells.  Glucagon has the greatest effect on the liver although it affects many different cells in the body.  Glucagon's function is to cause the liver to release stored glucose from its cells into the blood.  Glucagon also the production of glucose by the liver out of building blocks obtained from other nutrients found in the body, for example, protein [4].


Blood glucose is normally maintained between 70 mg/dl and 110 mg/dl.  Blood glucose levels below 70mg/dl,  denote the situation of "hypoglycemia".   Although blood glucose levels of 110mg/dl can be normal, this is only the case if a meal has been taken within 2 to 3 hours.  A blood glucose level of 180mg/dl or more, is termed "hyperglycemia."  Diagnosis is made if blood glucose levels are above 200mg/dl after drinking a sugar-water drink (glucose tolerance test) [4]. 

Cell Types in the endocrine pancreas

                                 A                     B                             D                       PP

Peptide hormone:   glucagon             Insulin                 Somatostatin     Pancreaticpolypeptide

Molecular weight:     3500                 5800                       1500                     4200

Number of aa :          29                     51                          14                        36

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