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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 diabetes) and Type 2 (which used to be 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. There are uncommon genetically caused types as well.

Type 1 diabetes accounts for about  13 percent of cases of diabetes in the Australia (an estimated 158,900 people) which is 0.7% of Australian population. This is the most common cause in children. Most cases of type 1 diabetes are 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 (byproducts that result from the use of fat as an alternative energy source when glucose is unavailable). Type 1 diabetics make very little or no insulin. Any insulin producing beta cells 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. Type 1 diabetics 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.

Type 2 diabetes The number of people with type 2 diabetes is growing. This accounts for 85% of all cases of diabetes in Australia.  It is estimated to be present in over 4% of the population. Within 20 years, the number of people in Australia with type 2 diabetes may increase from an estimated 870,000 in 2014, to more than 2.5 million. The most socially disadvantaged Australians are twice as likely to develop diabetes.

Type 2 diabetics do make their own insulin but it is not in a sufficient amount to meet their needs because 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. It generally occurs later in life, in those who are obese, sedentary and over 45 years of age.

Risk factors for developing type 2 diabetes include;

  • Weight excess / obesity
  • Central or abdominal obesity
  • Lack of exercise
  • Family history of diabetes
  • Smoking
  • Long (>8 to 9 hours/day) duration of sleep
  • Dietary patterns - consumption of red meat, processed meat, and sugar sweetened beverages
  • Medical conditions - gestational diabetes, cardiovascular disease, hyperuricemia, polycystic ovary syndrome, metabolic syndrome
Abnormal glucose metabolism can be documented years before the onset of overt diabetes. For example the Oral Glucose Tolerance Test (OGTT-see Table) may identify individuals whose ability to handle a high glucose meal is not normal but is not sufficiently abnormal to identify them as diabetic e.g.  Impaired fasting glucose or impaired glucose tolerance (sometimes referred to as ‘pre-diabetes) Table. 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. Recognising these conditions is important as recent evidence shows that progression to diabetes can be markedly reduced by simple measures such as a small amount of weight loss and exercise.


Gestational diabetes or GDM is defined as glucose intolerance that begins or is first diagnosed during pregnancy. Most women with gestational diabetes mellitus are normoglycemic after delivery. GDM generally develops and is diagnosed in the late second or early third trimester of the pregnancy. It may appear earlier, particularly in women with a high level of risk for GDM. GDM affects about 10 – 14% of pregnancies in Australia..

The prevalence is affected by maternal factors such as history of previous gestational diabetes, ethnicity, advanced maternal age, family history of diabetes, pre-pregnancy weight and high gestational weight gain. Mothers of different ethnicity born in areas with high diabetes prevalence such as Polynesia, Asia and the Middle East, are three times as likely to have GDM as mothers born in Australia. Among Aboriginal and Torres Strait Islander mothers, GDM is twice as common, and pre-gestational diabetes affecting pregnancy is three to four times as common as in non-Indigenous mothers.

In pregnancy, there is a natural increase in levels of hormones including cortisol, growth hormone, human placental lactogen, and progesterone and prolactin levels, causing two to three fold increases in insulin resistance. The action of these hormones is usually compensated by increased insulin release. In pregnant women with abnormal glucose tolerance or impaired β-cell reserve, the pancreas is unable to sufficiently increase insulin secretion in order to control blood glucose.

In Australia, gestational diabetes is usually diagnosed by an oral glucose tolerance test performed between the 24th and 28th week of pregnancy or earlier if the woman is at high risk. 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. Potential maternal complications during pregnancy and delivery include pre-eclampsia and higher rates of caesarean delivery, maternal birth injury, and postpartum haemorrhage. Gestational diabetes also raises the risk of eventually developing type 2 diabetes, for both the mother and the baby.
 


Last Review Date: August 1, 2018