Diabetes Mellitus Type 2 (non-insulin dependent, mature age onset)

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What is Diabetes Mellitus Type 2?

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Type 2 Diabetes Mellitus is a chronic metabolic syndrome defined by resistance to the hormone insulin. This leads to inappropriate hyperglycaemia (increased blood sugar levels) and deranged metabolism of carbohydrate, fats and proteins. Insulin is a key metabolic hormone secreted by the pancreas. Insulin exerts its actions in the liver and peripheral tissues such as muscle and fat. In type 2 diabetes mellitus, relative insulin deficiency usually occurs because of resistance to the actions of insulin in muscle, fat, and the liver. This abnormality results in decreased glucose transport in muscle, increased liver glucose production, and increased breakdown of fat.

Type 2 diabetes mellitus is also known as Non Insulin Dependent Diabetes Mellitus (NIDDM). This name is no longer used as some patients with type 2 diabetes mellitus do require insulin treatment in advanced stages.

Who gets Diabetes Mellitus Type 2?

Diabetes is a common condition in the Australian community. Approximately one quarter of Australians over the age of 25 years have diabetes or its precursor known as impaired glucose tolerance. Both these conditions increases one's risk of heart disease. Type 2 diabetes mellitus is by far the most common form of diabetes, accounting for 85-90% of all those diagnosed with diabetes mellitus.

Rates are increasing at alarming rates presumably due to the aging population and increased rates of obesity. Approximately 7.5% of Australians over the age of 25 years suffer from type 2 diabetes mellitus. Another 10% have a pre-diabetic condition called impaired glucose tolerance, and about a third of these patients will go on to develop overt diabetes within 10 years.

The incidence of type 2 DM increases with age. Most patients develop the disease after 40 years of age. Overall, males and females seem to be equally affected. The incidence of type 2 DM differs throughout the world, probably due to environmental, genetic and behavioural factors. People with Indian, Pacific Islander or Australian Aboriginal heritage are at particularly high risk of developing type 2 diabetes.

Children

While type 2 DM usually affects patients over 40 years of age, more and more younger people, even children, are now developing type 2 diabetes. The increasing number of young people who are overweight, with sedentary lifestyles, increases the incidence of type 2 diabetes mellitus in this age group.

Predisposing Factors

In type 2 diabetes, peripheral resistance to the actions of insulin is combined with a pancreatic secretory deficiency of varying severity. Insulin resistance means the body is unable to take glucose (sugar) up into cells. Normally, the body would compensate for this by producing increased amounts of insulin, but in type 2 diabetes mellitus the pancreas cannot respond. This means not enough insulin is produced, and excess sugar remains in the bloodstream (hyperglycemia) instead of being taken up into cells and used for energy.

Type 2 diabetes is partly a genetic disease and partly a lifestyle disease. While some people have a genetic predisposition to diabetes, they may not actual develop the disease without 'lifestyle' triggers such as excess fat and sugar intake or inadequate physical exercise.

While there is no single cause for developing Type 2 diabetes, there are well-known risk factors. Some of these can be changed (avoidable) and some cannot (unavoidable).

Unavoidable risk factors

A family history of diabetes. Identical twins of an affected person have more than 80% chance of developing diabetes, and 25% of patients have an affected first degree relative.
Age - people greater than 45 years have higher rates of disease. The risk increases as we get older.
Ethnic background - Aboriginal or Torres Strait Islander men, and people with Melanesian, Polynesian, Chinese or Indian background are more likely to develop type 2 diabetes mellitus.
Having Polycystic Ovarian Syndrome or a history of gestational diabetes during pregnancy.
Low birth weight is thought to predispose to diabetes due to poor beta-cell development and function.

Avoidable risk factors

Obesity (Click the relevent links to explore possible treatment options to combat obesity: meal replacement programs, lifestyle changes, drugs and surgery).
Physical inactivity
High blood pressure
Diet
Cholesterol
Smoking

Progression

Type 2 diabetes mellitus may have an onset over several months, or be asymptomatic and be detected on a routine blood test. It is generally not recognised and diagnosed until the patient seeks health care for another problem.

Some common presenting symptoms of type 2 diabetes mellitus include:

Excessive thirst.
Increased urine output (polyuria).
Hunger.
Weight loss or gain.
Slow healing or frequent infections.
Blurred vision.
Dry eyes
Headaches.
Numbness, tingling or burning of the feet (peripheral neuropathy).

Without treatment patients may develop acute complications due to dehydration (HONKC, see below) and long-term complications will develop much more rapidly.

The main acute complication is hyperosmolar nonketotic coma (HONKC), sometimes also known as hyperosmolar hyperglycaemic nonketotic coma (HHNC). This is a condition that develops over several days in poorly controlled diabetes involving high blood glucose and potentially lethal secondary dehydration and electrolyte disturbances.

Long-term complications include:

Microvascular disease:
- Diabetic retinopathy (eye disease).
- Diabetic nephropathy (kidney disease).
- Peripheral neuropathy and autonomic neuropathy (nerve disease).
- Impotence (difficulty maintaining an erection).
Macrovascular disease - i.e. atherosclerosis (hardening of the arteries) causing:
- Coronary artery disease or heart attack.
- Cerebrovascular disease (stroke).
- Peripheral vascular disease - potentially causing gangrene and leading to need for leg or toe amputation.