Difference Between Insulin and Glucagon

Main Difference – Insulin vs Glucagon

Insulin and glucagon are two types of hormones responsible for the maintenance of glucose levels in the blood. Glucose is one of the vital sources of energy. It circulates through blood and is taken up by the metabolizing cells of the body. Both enzymes are secreted by the pancreas. The main difference between insulin and glucagon is that insulin increases the glucose uptake by the body cells from the blood whereas glucagon releases glucose from the liver and muscle cells into the blood. This means insulin decreases the blood glucose levels while glucagon increases the blood glucose level.

Key Areas Covered

1. What is Insulin
      – Definition, Role, Associated Diseases
2. What is Glucagon
      – Definition, Role, Associated Diseases
3. What are the Similarities Between Insulin and Glucagon
      – Outline of Common Features
4. What is the Difference Between Insulin and Glucagon
      – Comparison of Key Differences

Key Terms: Diabetes, Glucagon, Gluconeogenesis, Glycogenesis, Glycogenolysis, Glucose, Insulin, Hormones, Liver, Pancreas

What is Insulin

Insulin is a hormone produced by β cells of the pancreas. It decreases the glucose levels in the blood. The stimulus that induces the secretion of insulin is the high glucose concentrations in the blood. Once the glucose concentration comes to the normal level, the levels of insulin in the blood are also reduced. The normal level of glucose in the blood is 70 to 100 mg/dL. The influence of insulin on glucose is shown in figure 1.

Figure 1: Influence of Insulin on Glucose

Insulin affects the cells of the body such as skeletal muscle cells, liver cells, and fat cells. Insulin stimulates these cells to take the glucose from the blood. This reduces the blood glucose levels. Inside the cells, the catabolism and the storage of glucose are also induced by insulin. Glycogenesis is the synthesis of glycogen from glucose in the liver. Insulin stimulates the synthesis of triglycerides from free fatty acids. When the glucose levels are high in the blood, the secretion of glucagon is inhibited. Insulin deficiency causes both type 1 and type 2 diabetes.

What is Glucagon

Glucagon is a hormone produced in α cells of the pancreas and stimulates the breakdown of glycogen. The stimulus that induces the secretion of glucagon from the pancreas is the low concentration of glucose in the blood. Blood glucose levels can be decreased between meals and during exercise. The action of glucagon is shown in figure 2.

Figure 2: Action of Glucagon

Glucagon mostly affects liver cells. It releases glucose from glycogen into the bloodstream. The process of breaking down glycogen in the liver is referred to as glycogenolysis. Glucagon stimulates the synthesis of glucose from non-carbohydrate carbon substrate such as amino acids in gluconeogenesis. Glucagon deficiency causes hypoglycemia and glucagonoma.

Similarities Between Insulin and Glucagon

Both insulin and glucagon are two hormones that regulate blood glucose levels.
Both insulin and glucagon are secreted by the pancreas.
Both insulin and glucagon are peptide hormones.

Definition

Insulin: Insulin is a hormone produced by β cells of the pancreas and decreases the glucose levels in the blood.

Glucagon: Glucagon is a hormone produced in the α cells of the pancreas and stimulates the breakdown of glycogen.

Secretion

Insulin: Insulin is secreted by the red color β islet cells of the pancreas.

Glucagon: Glucagon is secreted by the green color α islet cells of the pancreas.

Activation

Insulin: Insulin becomes active when the blood glucose level is high.

Glucagon: Glucagon becomes active when the blood glucose level is low.

Function

Insulin: Insulin stimulates the uptake of glucose and amino acids into the cells.

Glucagon: Glucagon stimulates the release of fatty acids from the triglycerides, which are stored in the body.

Liver Glycogen

Insulin: Insulin stimulates the synthesis of glycogen by increasing glucose uptake by the liver.

Glucagon: Glucagon stimulates glycogenolysis and release of glucose from the liver.

Fatty Acids

Insulin: Insulin stimulates the synthesis of triglycerides from free fatty acids.

Glucagon: Glucagon stimulates the release of fatty acids from the triglycerides.

Liver Gluconeogenesis

Insulin: Insulin inhibits gluconeogenesis.

Glucagon: Glucagon stimulates gluconeogenesis and release of glucose from the liver.

Skeletal Muscles

Insulin: Insulin stimulates the uptake and storage of glucose in skeletal muscles.

Glucagon: Glucagon has no effect on skeletal muscles.

Amino Acid Uptake

Insulin: Insulin stimulates the uptake of amino acids by body cells.

Glucagon: Glucagon has no effect on amino acids.

Hypothalamus

Insulin: Insulin reduces hunger by regulating the hypothalamus.

Glucagon: Glucagon has no effect on the hypothalamus.

Diseases

Insulin: Insulin deficiency causes type 1 and type 2 diabetes.

Glucagon: Glucagon deficiency causes hypoglycemia and glucagonoma.

Conclusion

Insulin and glucagon are two hormones that regulate the levels of glucose in the blood. Both insulin and glucagon are secreted by different types of cells in the pancreas. Insulin decreases blood glucose levels and glucagon increases glucose in the blood. The main difference between insulin and glucose is the influence of each hormone on the concentration of glucose in the blood.

Reference:

1. “What is Insulin?” EndocrineWeb, Available here.
2. Ogbru, PharmD Omudhome. “Glucagon: Function, Side Effects & Dosage.” MedicineNet, Available here.
3. “Normal Regulation of Blood Glucose.” EndocrineWeb, Available here.

Image Courtesy:

1. “Insulin glucose metabolism ZP” By XcepticZP at en.wikipedia (Public Domain) via Commons Wikimedia
2. “Glucagon Activation” By FrozenMan – Own work (CC BY-SA 4.0) via Commons Wikimedia