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Table 20-4.
Comparison of type 1 and type 2 diabetes. |
| Body_ID: None |
| Comparison of type 1 and type 2 diabetes mellitus |
| Body_ID: T020004.50 |
| | Type 1 | Type 2 |
| Body_ID: T020004.100 |
| Onset | usually under 20 years of age | usually over 40 years of age |
| Body_ID: T020004.150 |
| | | |
| Body_ID: T020004.200 |
| Insulin synthesis | absent: immune destruction of β-cells | preserved: combination of impaired β-cell function and insulin |
| Body_ID: T020004.250 |
| Plasma insulin concentration | low or absent | low, normal, or high |
| Body_ID: T020004.300 |
| Genetic | inheritance | not associated with HLA, |
| Body_ID: T020004.350 |
| susceptibility | associated with HLA antigens | polygenic |
| Body_ID: T020004.400 |
| Islet cell antibodies at diagnosis | yes | no |
| Body_ID: T020004.450 |
| Obesity | uncommon | common |
| Body_ID: T020004.500 |
| Ketoacidosis | yes | possible as a result of major stress |
| Body_ID: T020004.550 |
|
| Body_ID: T020004.600 |
Type 1 diabetes was formerly known as insulin-dependent diabetes, IDDM, or juvenile diabetes, and type 2 diabetes was described as noninsulin-dependent diabetes, NIDDM, or maturity-onset diabetes.
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|
Table 20-5.
Diagnostic criteria for diabetes mellitus and glucose intolerance. |
| Body_ID: None |
Diagnosis of diabetes mellitus and glucose intolerance |
| Body_ID: T020005.50 |
| Condition | Diagnostic criteria (mmol/L) | Diagnostic criteria (mg/dL) | Comments |
| Body_ID: T020005.100 |
| normal fasting plasma glucose | below 6.1 | below 110 | |
| Body_ID: T020005.150 |
| impaired fasting glucose (IFG) | equal or above 6.1 but below 7.0 | equal or above 110 but below 126 | |
| Body_ID: T020005.200 |
| impaired glucose tolerance (IGT) | plasma glucose 2 h after 75 g load 7.8 or above, but below 11.1 | plasma glucose 2 h after 75 g load 140 or above, but below 200 | diagnosed during OGIT |
| Body_ID: T020005.250 |
| diabetes mellitus* | | | |
| Body_ID: T020005.300 |
| criterion 1 | random plasma glucose 11.1 or above† | random plasma glucose 200 or above† | |
| Body_ID: T020005.350 |
| criterion 2 | fasting plasma glucose 7.0 or above | fasting plasma glucose 126 or above | |
| Body_ID: T020005.400 |
| criterion 3 | 2 h value during OGTT 11.1 or above | 2 h value during OGTT 200 or above | |
| Body_ID: T020005.450 |
*If one of the criteria is fulfilled, diagnosis is provisional. The diagnosis needs to be confirmed next day using a different criterion.
†If accompanied by symptoms (polyuria, polydypsia, unexplained weight loss). These are the criteria proposed by the American Diabetes Association in 1997 (see Further Reading).
|
| Type 1 diabetes develops in young people, with the peak incidence at approximately 12 years of age. It is caused by autoimmune destruction of pancreatic β-cells. The precipitating cause is still unclear. It could be that a viral infection initiates the autoimmune reaction. Alternatively, a cytokine response to viral infection, or to another insult, could attract monocytes and macrophages that infiltrate and destroy the
pancreatic islets. In addition to the inflammatory infiltration of the islets, a proportion of patients have antibodies against β-cell proteins. These are often present before the diagnosis of diabetes. Circulating autoantibodies to insulin itself are also present in some individuals.
|
| The susceptibility to type 1 diabetes appears to be inherited, however, no 'diabetes gene' has yet been discovered. The best investigated susceptibility gene is located on chromosome 6 in the major histocompatibility complex (MHC) that codes for immune system recognition molecules known as histocompatibility antigens (HLA) (see Chapter 36). Susceptibility to type 1 diabetes is associated with HLA types DR4 and DQw8, whereas DR2 and DQw1.2 appear to suppress the tendency to develop the disease. The sibling of a type 1 diabetic patient has a 10% chance of developing diabetes by the age of 50 years.
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