Diabetes
Diabetes arises because the body can't use glucose properly, either because of a lack of the hormone insulin or because the insulin available doesn't work effectively. Not only is excess sugar found in the blood but it may appear in the urine too.
The full name 'diabetes mellitus' comes from the Greek word 'diabetes' meaning siphon - to pass through, and 'mellitus,' the Latin for honeyed or sweet. It refers to a major symptom of diabetes , sugar in the urine.
Types of Diabetes
There are two main types of diabetes:
- In type 1, the body cannot produce insulin. This usually starts in childhood or young adulthood. It's treated with diet control and insulin injections. type 1 diabetes used to be called 'insulin-dependent diabetes'.
- In Type 2 diabetes, not enough insulin is produced or the insulin that is made doesn't work properly. It tends to affect people as they get older, and usually appears after the age of 40. It used to be known as 'maturity-onset diabetes' or 'non-insulin dependent diabetes (NIDDM)
Normal Blood Sugar Control
In the body, glucose is converted into energy. This glucose comes ready-made in sweet foods such as sweets and cakes, or from starchy foods such as potatoes, pasta or bread when they're digested. The liver is also able to manufacture glucose.
Under normal circumstances the hormone insulin, which is made by the pancreas, carefully regulates how much glucose is in the blood. Insulin stimulates cells to absorb enough glucose from the blood for the energy, or fuel, that they need. Insulin also stimulates the liver to absorb and store any glucose that's left over. After a meal the amount of glucose in the blood rises, and this triggers the release of insulin. When blood glucose levels fall, during exercise for example, insulin levels fall too. A second hormone manufactured by the pancreas is called glucagon. It stimulates the liver to release glucose when it's needed, and this raises the level of glucose in the blood.
Insulin is manufactured and stored in the pancreas, which is a thin gland about 15cm (6in) long that lies crosswise behind the stomach. It's often described as being two glands in one, since in addition to making insulin it also produces enzymes that are vital for digestion of food. These include lipase, which helps to digest fat, and amylase that helps to digest starchy foods. It also releases 'bicarbonate of soda' to neutralise any stomach acid that may otherwise damage the lining of the gut.
Causes
Type 1
In type 1 diabetes the cells in the pancreas that make insulin are destroyed, causing a severe lack of insulin. This is thought to be the result of the body attacking and destroying its own cells in the pancreas - known as an autoimmune reaction.
It's not clear why this happens, but a number of explanations and possible triggers of this reaction have been proposed. These include:
- infection with a specific virus or bacteria
- exposure to food-borne chemical toxins
- exposure as a very young infant to cow's milk, where an as yet unidentified component triggers the autoimmune reaction
However, these are only hypotheses and are by no means proven causes.
Type 2
In this type of diabetes the receptors on cells in the body that normally respond to the action of insulin fail to be stimulated by it - this is known as insulin resistance. In response to this more insulin may be produced, and this overproduction exhausts the insulin-manufacturing cells in the pancreas; there is simply insufficient insulin available; and the insulin that is available may be abnormal and therefore doesn't work properly.
The following risk factors increase the chances of someone developing type 2 diabetes:
- increasing age
- obesity
- physical inactivity
Rarer causes of diabetes include:
- certain medicines
- pregnancy (gestational diabetes)
- any illness or disease that damages the pancreas and affects its ability to produce insulin, such as pancreatitis
