Glucagon and Insulin – Regulators of Glucose

Glucagon and Insulin are both hormones produced and excreted by the same organ, the pancreas. There are regions in the pancreas called the islets of Langerhans where you can find the alpha cells responsible for producing Glucagon and the beta cells that produce Insulin. These two hormones work in tandem to maintain healthy levels of blood glucose.

Under normal circumstances, the level of insulin is determined by the amount of glucose in the blood plasma. So, when blood sugar rises the beta cells in the pancreas are triggered to release insulin so that glucose can be transported to our cells for energy. When blood sugar levels are low, the circulation of insulin ceases. This response is what is needed to maintain blood glucose levels within normal narrow range.

Whereas insulin secretion is triggered by high blood sugar, the presence of Glucagon is initiated by low blood glucose levels. It prompts the liver to start breaking down sugar stored there in the form of glycogen. Once glycogen is broken down to glucose, it is then released into the blood stream where it is transported to cells with the help of insulin for energy production.  In certain situations, glucagon can induce the liver and muscles to synthesize glucose from non-carbohydrate sources such as proteins.

From the foregoing, insulin has two main functions in the body:

  • Promotes entry of glucose into the cells and also supports the synthesis of lipids. This essentially ‘mops’ up excess sugar from the plasma glucose.
  • Prevents mechanisms that would flood the bloodstream with excess glucose. This includes inhibition of glycogen, lipids and proteins breakdown. It also prevents the buildup of ketone bodies which usually happens when fats are broken down for energy. — KETOACIDOSIS

Function of Glucagon:

  • Glucagon is a hormone that responds to low blood glucose levels by breaking down the macromolecule glycogen into the smaller molecules we know as glucose and releasing it into the blood stream. Glucagon brings blood sugar up while Insulin brings blood sugar down.
  • Induces lipolysis which is the breakdown of lipids into free fatty acids

Terminology used to describe levels of Insulin

Hypoinsulinemia

Refers to insulin levels in the blood that are lower than what is considered normal. This situation leads to insufficient glucose uptake by the body cells and subsequent rise in blood sugar. Many patients with diabetes type 2 experience low insulin levels. The primary reason for this is usually a problem with the beta cells in the islets of Langerhans responsible for the production of insulin.

If there is no insulin at all, insulin injections have to be given. This is commonly seen in patients with diabetes type 1.

Hyperinsulinemia

Indicates an abnormally high level of blood glucose. The causes include disorders of glucose metabolism. It can also occur during administration insulin injections to battle diabetes. A miscalculation in insulin treatments can lead to excess levels of insulin in the blood stream which can result in a sudden drop in blood glucose levels – hypoglycemia.

Another culprit for hyperinsulinemia are insulinomas. Insulinomas are pancreatic tumors that secrete excess insulin which leads to chronic low blood sugar. High insulin levels are also seen in conditions such as metabolic syndrome where insulin level is unusually high but ineffective.

Insulin resistance

This occurs when insulin level is normal, or even raised, but for some reason it is not effective in the metabolism of glucose, the cells of the body become “resistant” to the effects of insulin. This leads to uncontrolled high blood glucose despite the relatively high circulating insulin. This is one of the causes of diabetes type 2 and a common sign in metabolic syndrome.

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