Diabetes and the need for insulin replacement therapy
Diabetes
Diabetes (full medical term 'diabetes mellitus') is a condition in which the level of glucose (sugar) in the blood is higher than normal. The blood glucose level is normally controlled by the hormone insulin, which is produced by special cells - beta cells - found within the pancreas.
There are two main types of diabetes:
- Type 1 diabetes - the insulin producing beta cells have been destroyed and no insulin is produced.
- Type 2 diabetes - insulin is produced but does not work efficiently and often not enough insulin is produced to keep blood glucose levels within normal limits.
Insulin and blood glucose
Glucose in the blood comes from two main sources:
- The liver - glucose is stored in the liver and released into the bloodstream during periods of fasting (between meals and, especially, overnight).
- Dietary carbohydrates - most carbohydrate foods are broken down by digestive enzymes into glucose, which is absorbed from the intestine into the bloodstream about 1- 2 hours after eating.
Insulin allows the body's cells to take in glucose from the blood and use it to fuel energy needs. It acts rather like a key, unlocking the doors on the surface of cells and letting glucose in. If insulin is either absent, or not working properly, then cells can't access the glucose in the blood and the blood glucose level rises.
High blood glucose levels
As the blood glucose level rises, the kidney starts to filter out excess glucose into the urine. This, in turn, draws extra water into the urine and causes the person to become dehydrated and thirsty. Excessive urination and thirst are common signs of undiagnosed or poorly controlled - diabetes.
Lack of insulin
When insulin is lacking, cells are unable to obtain glucose from the blood to use for energy. The body has to turn to alternative fuels - fats and protein - in an attempt to keep going. This is a perfectly natural response, however the body is not designed to burn these fuels on a large scale. Using fats as an energy source produces chemicals, known as ketones, as by-products. When ketones are produced in excess, they build up in the blood and cause the blood to become too acidic. This is a dangerous condition known as diabetic ketoacidosis (DKA) and requires immediate medical attention. DKA is effectively caused by a lack of insulin
Diabetes management and insulin
Normal insulin production
In non-diabetic people, insulin is automatically released from the pancreas in response to a
rise in blood glucose following a meal. This allows the glucose to be taken up by the body's
cells where it is either used straight away, or stored (mostly in the liver or muscles) for
later. So, in the presence of insulin, glucose is removed from the blood and the blood
glucose level drops again. Just the right amount of insulin is produced to keep the blood
glucose level within normal limits. In addition to this, small amounts of insulin are
continuously produced between meals and overnight, in order to keep the body ticking over.
Insulin therapy for people with diabetes
People with Type 1 diabetes produce no insulin and therefore depend on insulin injections to stay alive. People with Type 2 diabetes usually produce some insulin and many are treated with diet and tablets that enable them to make better use of the insulin that they produce. In some people with Type 2 diabetes, insulin production decreases as the years go by and these people may need to start having insulin injections in order to stay healthy.
The aim of diabetes management is too keep blood glucose levels close to normal. For those people who require insulin, this means coordinating insulin injections with meals and snacks, whilst counterbalancing the effects of activity levels.
There are a number of ways in which insulin is used to treat people with diabetes. Most insulin injection regimens use a combination of short acting and longer acting insulin. The timing and dosages of the injections are aimed to supply the body's natural insulin needs as far as possible.