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Types of Diabetes

There are two main types of diabetes: Type 1 (which used to be called insulin dependent diabetes or juvenile onset diabetes) and Type 2 (which used to known as non-insulin dependent diabetes or adult onset diabetes). In addition, Gestational Diabetes is a term used to describe diabetes which is recognised for the first time during pregnancy. Pancreatic disease or damage can also cause diabetes if the insulin producing beta cells are destroyed.

Type 1 diabetes develops if the body can no longer produce insulin. It accounts for approximately 10% of diabetes cases in the United Kingdom and is usually diagnosed in those under the age of 30. Symptoms often develop abruptly and the diagnosis is often made following an emergency admission to hospital. The patient may be seriously ill, even unconscious, with very high glucose levels and high levels of ketones.
Patients with Type 1 diabetes make very little or no insulin. Any insulin producing beta cells that patients have at the time of diagnosis are usually completely destroyed within 5 to 10 years leaving them entirely reliant on insulin injections. The exact cause of type 1 diabetes is unknown, but a family history of diabetes, viruses that injure the pancreas, and autoimmune processes (where the body's own immune system destroys the beta cells) are all thought to play a role. As type 1 diabetes has an earlier age of onset and hence longer duration, patients may have more severe medical complications than other forms of diabetes. For instance, currently 40% of those with type 1 diabetes develop serious kidney problems leading to kidney failure by the age of 50.

Those with Type 2 diabetes do make their own insulin but it is either not in a sufficient amount to meet their needs and/or their body has become resistant to its effects. At the time of diagnosis they may have typical symptoms of diabetes, especially thirst, weight loss or may be passing large amounts of urine or they may not have any symptoms, and diagnosis may be made on finding high glucose concentrations in the blood. About 90% of diabetes cases in the United Kingdom are type 2. It generally occurs later in life, in those who are obese, sedentary and over 45 years of age. Risk factors include:

  • Weight excess / obesity
  • Lack of exercise
  • A family history of diabetes
  • Any abnormality of glucose tolerance – the oral glucose tolerance test (OGTT) may identify individuals whose ability to handle a high glucose meal is not normal but is not sufficiently abnormal to identify them as Diabetic
  • Ethnic groups - more common in Asian and African-Caribbean communities
  • Gestational diabetes during pregnancy or baby weighing more than 9 pounds
  • High blood pressure
  • High triglycerides, high cholesterol, low HDL

Because the population of the western world is becoming more obese and not getting enough regular exercise, the number of those developing type 2 diabetes is rising and, of particular concern is its development in young people.

Gestational diabetes is usually a temporary type of hyperglycaemia (high blood glucose concentration) seen in some pregnant women, usually during the second or third trimester. The cause is unknown, but it is thought that some hormones from the placenta increase insulin resistance in the mother causing elevated blood glucose levels. In the UK, gestational diabetes is usually diagnosed by an oral glucose tolerance test carried out, either because high glucose concentrations have been found in the urine or blood or because the women is known to be at risk for the condition (obesity, a family history of Type 2 diabetes, an unexplained stillbirth or neonatal death in a previous pregnancy, a very large infant in the current or a previous pregnancy). Testing is usually performed between the 24th and 28th week of pregnancy. If gestational diabetes is not treated, the baby is likely to be larger than normal, be born with low glucose levels, and be born prematurely. Gestational diabetes also raises the risk of eventually developing type 2 diabetes, for both the mother and the baby.

Impaired fasting glycaemia or impaired glucose tolerance (sometimes referred to as "pre-diabetes") are conditions which can only be detected by use of the oral glucose tolerance test and are characterised by glucose levels that are higher than normal, but not high enough to be diagnostic of diabetes. Usually these individuals do not have any symptoms but if nothing is done to lower their glucose levels, they are at great risk of developing diabetes in the future. Recognising these conditions is important as recent evidence shows that progression to diabetes can be markedly reduced by simple measures such as weight loss and increased exercise.

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