4.3. Describe the function of insulin

This guide will help you answer 4.3. Describe the function of insulin.

Insulin is a hormone produced by the pancreas, an organ located near the stomach. It plays a key role in regulating blood sugar levels, ensuring that the body has enough energy to function properly while avoiding excessive sugar in the bloodstream. Insulin works together with glucagon to maintain balance, with insulin responsible for lowering glucose levels when they are too high.

Where Insulin Comes From

Insulin is produced by the beta cells of the pancreas. These cells are found in small clusters known as the islets of Langerhans. After eating, the pancreas constantly monitors blood sugar levels. When these levels rise—particularly after consuming carbohydrates—the beta cells release insulin into the bloodstream.

How Insulin Works

Insulin’s main role is to lower blood sugar levels by helping the body’s cells absorb glucose. Glucose, a type of sugar, is the body’s preferred source of energy. For cells to use glucose, they need insulin to “unlock” the cells and allow the glucose to enter.

Here’s how insulin operates:

• Promoting Glucose Absorption: Once insulin is released, it attaches to receptors on the surface of the body’s cells. This action “opens the door” for glucose to move from the bloodstream into the cells where it can be used for energy.
• Encouraging Storage: When the body doesn’t immediately need the glucose for energy, insulin directs the liver, muscles, and fat cells to store the excess glucose. In the liver and muscles, it is stored as glycogen (a complex carbohydrate). In fat cells, it is stored as fat.
• Stopping Glucose Production: Insulin also signals the liver to reduce its production of glucose. This is important, as the liver naturally releases stored glucose into the bloodstream between meals to keep energy levels stable.

By performing these actions, insulin helps prevent blood sugar levels from rising too high after meals, a condition known as hyperglycaemia.

When Insulin is Released

After eating, particularly foods that are high in carbohydrates, blood sugar levels increase. This rise signals the pancreas to release insulin. Insulin secretion begins within minutes of starting a meal and lasts for several hours while the body digests and absorbs the food.

In addition to mealtimes, small amounts of insulin are released consistently throughout the day and night. This steady release helps maintain stable blood sugar levels when the body is not eating, such as between meals or while sleeping.

The Balance Between Insulin and Glucagon

Insulin works in opposition to glucagon, another hormone produced by the pancreas. While insulin lowers blood sugar by helping cells absorb and store glucose, glucagon has the opposite effect, raising blood sugar by prompting the liver to release glucose into the bloodstream.

These two hormones constantly adjust in response to the body’s needs. After a meal, insulin levels rise and glucagon levels drop, helping to store or use the glucose from the food. When blood sugar levels fall, such as during fasting or exercise, glucagon levels increase and insulin levels decrease. This balance ensures the body maintains enough energy without allowing glucose levels to rise or fall too much.

The Importance of Insulin

Insulin is vital for ensuring the body’s cells can access glucose for energy. Without insulin, glucose builds up in the bloodstream, leading to hyperglycaemia. Long-term high blood sugar levels can damage various organs, including the heart, kidneys, eyes, and nerves.

On the other hand, if there is too much insulin in the blood or the body’s cells respond too strongly to insulin, it can cause hypoglycaemia (low blood sugar). Hypoglycaemia can be dangerous, leading to symptoms such as dizziness, confusion, and in severe cases, loss of consciousness.

Insulin and Diabetes

Diabetes is a condition where the body cannot properly regulate blood sugar levels due to issues with insulin. There are two main types:

• Type 1 Diabetes: This occurs when the pancreas does not produce any or enough insulin. It is an autoimmune condition where the immune system attacks the beta cells in the pancreas. People with type 1 diabetes need to take insulin injections or use an insulin pump to manage their blood sugar levels.
• Type 2 Diabetes: In this form, the body produces insulin, but the cells become resistant to it. This means the cells do not respond properly, and glucose remains in the bloodstream. Type 2 diabetes is often managed with diet, exercise, oral medications, or insulin therapy in some cases.

In both types of diabetes, poor blood sugar management can lead to complications. These include kidney disease, vision loss, and increased risk of heart attacks and strokes. Health and social care workers supporting individuals with diabetes need to understand insulin’s role to help manage the condition effectively.

The Role of Insulin in Fat and Protein Metabolism

In addition to regulating blood sugar, insulin has other effects on how the body uses and stores nutrients. It plays a part in fat and protein metabolism:

• Fat Storage: When insulin levels are high, the body is in “storage mode.” Excess glucose is converted into fat and stored in adipose tissue. Insulin also inhibits the breakdown of stored fat, favouring fat storage over fat usage.
• Protein Synthesis: Insulin helps stimulate the uptake of amino acids by cells. Amino acids are the building blocks of proteins, so insulin supports muscle growth and repair.

What Happens When Insulin is Absent or Ineffective?

When insulin is absent, as in untreated type 1 diabetes, or when it is ineffective, as in type 2 diabetes, the body cannot use glucose properly. As a result:

• Blood sugar levels remain high, leading to hyperglycaemia.
• The body begins to break down fat for energy, producing ketones, which can lead to a dangerous condition called diabetic ketoacidosis (DKA). DKA can cause nausea, vomiting, dehydration, and in severe cases, coma or death.
• Over time, persistent high blood sugar damages blood vessels and organs, increasing the risk of severe complications.

In type 2 diabetes, the pancreas may try to “compensate” for insulin resistance by producing more insulin, but this can strain the pancreas. Over time, the pancreas may lose its ability to produce insulin altogether.

Medical Use of Insulin

Insulin therapy is an essential treatment for people with type 1 diabetes and for some with type 2 diabetes. It is usually delivered through injections or an insulin pump. Several types of insulin are available, including:

• Rapid-acting Insulin: Works quickly to manage blood sugar spikes after meals.
• Short-acting (Regular) Insulin: Takes slightly longer to act but still manages mealtime glucose rises.
• Intermediate-acting Insulin: Covers blood sugar needs for about half a day or overnight.
• Long-acting Insulin: Provides a steady release of insulin to manage blood sugar levels throughout the day or night.

Insulin therapy must be carefully balanced with food intake, physical activity, and blood sugar monitoring. Too much insulin can cause hypoglycaemia, while too little can lead to hyperglycaemia.

Final Thoughts

Insulin is a critical hormone that helps regulate blood sugar levels. It allows the body’s cells to absorb and use glucose for energy and directs excess glucose into storage. Without insulin, or if it doesn’t work properly, the body cannot maintain blood sugar balance. This can lead to serious health issues such as diabetes and its complications.

Understanding how insulin works is essential for health and social care workers supporting individuals with diabetes. It allows carers to spot signs of hypo- or hyperglycaemia and supports better management of the condition to prevent complications.