Type 1 diabetes

Type 1 diabetes occurs when the body's immune system destroys the insulin-producing cells, known as the beta cells, of the pancreas.

Normally the body's immune system fights off foreign invaders like viruses or bacteria. But in people with type 1 diabetes, the immune system attacks various cells in the body. We do not know why this happens, but it results in a complete deficiency of the insulin hormone.

Some people develop secondary diabetes, which is similar to type 1 diabetes. But with this type of diabetes, the beta cells are not destroyed by the immune system but by some other factor such as cystic fibrosis or pancreatic surgery.

Understanding insulin and type 1 diabetes

Normally the hormone insulin is secreted by the pancreas in low amounts. When you eat a meal, sugar (glucose) from food stimulates the pancreas to release insulin. The amount that is released is proportional to the amount that is required by the size of that particular meal.

Insulin's main role is to help move certain nutrients - especially sugar - into the cells of the body's tissues. Cells use sugars and other nutrients from meals as a source of energy to function.

The amount of sugar in the blood decreases once it enters the cells. Normally that signals the beta cells in the pancreas to lower the amount of insulin secreted so that you don't develop low blood sugar levels (hypoglycaemia). But the destruction of the beta cells that occurs with type 1 diabetes throws the entire process into disarray.

In people with type 1 diabetes, sugar isn't moved into the cells because insulin is not available. When sugar builds up in the blood instead of going into cells, the body's cells are starved of nutrients. This means other systems in the body must provide energy for many important bodily functions. As a result, high blood sugar develops and can cause:

• Dehydration. The build-up of sugar in the blood can cause you to urinate more as the level of glucose exceeds that which the kidneys can reabsorb, and the resultant glucose in the urine draws water with it. When the kidneys lose the glucose through the urine, a large amount of water is also lost, which causes dehydration.
• Weight loss. The loss of sugar in the urine means a loss of calories which provide energy. So, many people with high sugars lose weight. Dehydration also contributes to weight loss.
• Diabetic ketoacidosis (DKA). Without insulin and because the cells are starved of energy, the body breaks down fat cells. This produces acidic chemicals called ketones that can be used for energy. These ketones begin to build up in the blood and cause increased acidity. The liver continues to release the sugar it stores to help out. Since the body cannot use these sugars without insulin, more sugar piles into the blood stream. The combination of high excess sugars, dehydration and acid build-up is known as ketoacidosis, It can be life-threatening if not treated immediately.
• Damage to the body. Over time, the high sugar levels in the blood may damage the nerves and small blood vessels of the eyes, kidneys and heart. This can predispose a person to atherosclerosis (hardening and narrowing) of the large arteries that can cause heart attacks and stroke.