Diabetes is recognized as a group of heterogeneous disorders with the common elements of hyperglycemia and glucose intolerance, due to insulin deficiency, impaired effectiveness of insulin action, or both. Diabetes mellitus is classified on the basis of etiology and clinical presentation of the disorder in four types:
- type 1 diabetes
- type 2 diabetes
- gestational diabetes
- pre-diabetes
Type 1 - is sometimes called insulin-dependent, immune-mediated or juvenile-onset diabetes. It is caused by an auto-immune reaction, where the body's defense system attacks the insulin-producing cells. The beta cells of the pancreas produce little or no insulin, the hormone that allows glucose to enter body cells. The reason why this occurs is not fully understood.
The disease can affect people on any age, but usually occurs in children or young adults. People with this form of diabetes need injections of insulin every day in order to control the levels of glucose in their blood. Without insulin, people with type 1 diabetes will die.
Type 2 - is characterized by insulin resistance and relative insulin deficiency, either of which may be present at the time that diabetes becomes clinically manifest. The specific reasons for the development of these abnormalities are not yet known.
Diagnosis of type 2 diabetes usually occurs after the age of 40 years but could occur earlier, especially in populations with a high prevalence of diabetes. Type 2 diabetes can remain undetected for many year and the diagnosis is often made from associated complications or incidentally through an abnormal blood or urine glucose test.
Type 2 diabetes is often, but not always, associated with obesity, which itself can cause insulin resistance and lead to elevated blood sugar levels. It is strongly familial, but major susceptibility genes have not yet been indentified. There are several possible factors in the development of type 2 diabetes. These include:
- ethnicity
- obesity, diet and inactivity
- family history
- intrauterine environment (occurring while pregnant)
In contrast to type 1 diabetes, persons with type 2 diabetes are not dependent on exogenous insulin and are not ketosis-prone, but may require insulin for control of hyperglycemia if this is not achieved with diet alone or with oral hypoglycemic agents.
Type 2 diabetes constitutes about 85 - 95% of all diabetes in developed countries, and accounts for an even higher percentage in developing countries.
Gestational Diabetes - is a carbohydrate intolerance of varying degrees of severity which starts or is first recognized during pregnancy. The definition applies regardless of whether insulin is used for treatment or if the condition persists after pregnancy. It does not exclude the possibility that unrecognized glucose intolerance may have antedated the pregnancy.
Increased maternal glucose levels, are associated with an increased rate of complications in the baby, including large size at birth, birth trauma, hypoglycemia, and jaundice. Maintaining control of blood sugar levels significantly reduces the risks to the baby.
Women who have gestational diabetes have an increased risk of developing type 2 diabetes in later years. Gestational is also associated with increased risk of obesity and abnormal glucose metabolism during childhood and adult life in the offspring.
Pre-diabetes (Impaired Glucose Tolerance) - Impaired glucose tolerance is an asymptomatic condition defined by elevated (though not diabetic) levels of blood glucose two hours after a 75g oral glucose challenge. Along with impaired fasting glucose, it now recognized as being a stage in the transition from normality to diabetes.
Individuals with IGT are a high risk of progressing to type 2 diabetes, although such progression is not inevitable, and probably over 30% of individuals with IGT will return to normal glucose tolerance over a period of several years. Not surprisingly, IGT shares may characteristics with type 2 diabetes, being associated with obesity, advancing age, insulin resistance and an insulin secretory defect.
Insulin - is the internal secretion of the pancreas formed y groups of beta cells in the islets of Langerhans in this organ. It is the hormone needed to enable glucose to enter the cells and provide energy. Insulin is also important in keeping blood glucose levels within the acceptable limits.
Insulin is injected into the body by people with type 1 diabetes in whom the cells that produce insulin have destroyed. This is the most common form of diabetes in children and young adults, and they depend on insulin for survival. Insulin may also be used by people with type 2 diabetes. In type 2 diabetes, the body needs more insulin than it can produce.
(IDF - Diabetes Atlas Edition Three)
