| Fundamentals |
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| Diabetes mellitus is a syndrome characterized by chronic hyperglycaemia, resulting from defects in insulin secretion, insulin action or both. Clinical features include symptoms and signs primarily related to the severity of the metabolic disturbance, such as polyuria, polydipsia, weight loss, sometimes with polyphagia and blurred vision. The chronic hyperglycaemia diabetes is associated with long term dysfunction and failure of various organs especially eyes, kidneys, nerves, heart and blood vessels. |
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| Prevalence of Diabetes |
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| The prevalence of diabetes has a strong association with age, urbanization and ethnic group. In one of the age adjusted studies prevalence of diabetic was 8.2% in the urban & 2.4% in the rural population in Madras; but when the study was done in elderly people (age>60 years) diabetes was detected in 23.7% in urban & 9.9% in rural5. |
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| Classification of Diabetes |
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| Diabetes mellitus is an etiologically and clinically heterogeneous group of disorders that share hyperglycaemia in common. The overwhelming evidence in favour of this heterogenecity included the following : |
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- There are several distinct disorders, most of them rare, in which glucose intolerance is a feature.
- There are large differences in the prevalence of the major form of diabetes among various racial or ethnic groups worldwide.
- Patients with glucose intolerance present with great phenotype variation; for example, the difference between thin, ketosis-prone insulin dependent diabetes and obese, nonketotic, insulin-resistant diabetes.
- Evidence from genetic, immunological, and clinical studies shows that in western countries, the forms of diabetes that have their onset primarily in youth are distinct from those that have their onset mainly in adulthood.
- A type of non insulin-requiring diabetes in young people, inherited in an autosomal dominant fashion, is clearly different from the classic acute onset diabetes that typically occurs in the children.
- In tropical countries, several clinical presentation occur, including diabetes associated with fibrocalcific pancreatitis.
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| These and other lines of evidence were used to divide diabetes mellitus into five distinct type (IDDM, NIDDM, gestational diabetes mellitus [GDM], malnutrition related diabetes, and other types). The different clinical presentations and genetic and environmental etiologic factors of the five type permitted discrimination among them are as follows : |
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Table 1 |
Classification of Diabetes 1,3 |
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Type 1 |
Characterized by beta cell destruction, usually leading to absolute insulin deficiency. It has two forms :
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| Immune-mediated Diabetes mellitus : |
Results from a cellular mediated autoimmune destruction of the beta cells of the pancreas.
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| Idiopathic Diabetes mellitus : |
| Refers to forms of the disease that have no known etiologies. |
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Type 2 |
| Disease of insulin resistance that usually have relative (rather than absolute) insulin deficiency. |
| Can range from predominant insulin resistance with relative insulin deficiency to predominant insulin deficiency with some insulin resistance. |
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Impaired Glucose Homeostasis |
A metabolic stage intermediate between normal glucose homeostasis and diabetes. A risk factor for diabetes and cardiovascular disease. |
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Gestational Diabetes Mellitus |
Glucose intolerance in pregnancy
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| The definitions are unchanged |
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Other Specific Types |
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Diabetes caused by other identifiable etiologies. |
- Genetic defects of beta cell function (e.g., MODY 1,2,3)
- Genetic defects in insulin action
- Disease of the exocrine pancreas (e.g., cancer of the pancreas, cystic fibrosis, pancreatitis)
- Endocrinopathies (e.g., Cushing's?)
- Drugs or chemical induced (e.g., steroids?)
- Infection (e.g., Rubella, Coxsackie, CMV)
- Uncommon forms of immune-related diabetes
- Other genetic syndromes
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