Different kinds of diabetes
There are different kinds of Diabetes. Today we will speak about all the types of this disease, and what makes them different from each other.
Type I Diabetes
Type 1 diabetes is defined by the presence of ketosis caused by an almost complete lack of insulin or severe insulinopenia. Immunologic destruction of the beta cells is the etiologic basis of type I diabetes. An autoimmune cause is suggested by evidence of circulating antibodies to islet cells, to endogenous insulin, and/or to other antigen components of islet cells at the time of diagnosis.
Patients commonly are lean and have experienced considerable weight loss; almost all are diagnosed before age 20 years, although type I diabetes can develop at any age. Approximately 10% of all individuals who have been diagnosed with diabetes have type I diabetes. Daily insulin injections are required throughout the patient’s life to prevent ketoacidosis and death.
Type II Diabetes
Type II diabetes is the most common type of diabetes, accounting for 85% to 90% of all diagnosed cases in the United States, and is more prevalent among various non-Caucasian ethnic/racial populations, such as American Indians, African Americans, Pacific Islanders, and Hispanics.
A strong genetic basis exists for type II diabetes (approximately 90% of patients with type II diabetes have a positive family history of this disorder). In addition, identical twin studies have revealed a 60% to 90% concordance for diabetes.
An absence of ketosis is one of the primary features that distinguishes type II diabetes from type I diabetes, although it is possible to have ketonemia with type II diabetes.
Patients with type II diabetes can vary considerably in their ability to secrete insulin. Insulin secretion, however, is inadequate to overcome the insulin resistance associated with this type of diabetes. Defects of insulin action (insulin resistance) are typical of type II diabetes.
Obesity is strongly associated with type II diabetes. Approximately 90% of people with type II diabetes are obese (20% over ideal body weight) and the chances of developing type II diabetes double for every 20% increase in body weight in susceptible individuals.
However, type II diabetes also can develop in non-obese individuals; this is more commonly observed in older patients. The incidence of type II diabetes increases with age and obesity in part because people tend to gain weight and especially develop central abdominal obesity as they age.
Type II diabetes usually is diagnosed after the age of 40, although it may be diagnosed more frequently at a younger age (eg, 30 years old) in certain ethnic groups prone to developing diabetes. Patients are usually asymptomatic and only occasionally display the classic symptoms of diabetes mellitus (polydipsia, polyuria, polyphagia, weight loss). Because type II diabetes can go unrecognized for many years, early stages of microvascular disease and frank macrovascular complications may be present by the time a diagnosis is made.
Impaired Glucose Tolerance
Individuals who have plasma glucose levels that are higher than normal but lower than established diagnostic values for diabetes mellitus are classified as having IGT. This condition is common (approximately 11% of the US population) and considered a precursor of type II diabetes.
Although individuals with IGT are more likely to eventually develop diabetes mellitus, only approximately 25% do develop type II diabetes and a similar percentage subsequently have normal glucose levels. The rate of progression is approximately 5% to 10% per year and can be influenced by:
- Ethnic origin
- Degree of obesity
- Distribution of body fat
- Sedentary lifestyle
- Concomitant medical conditions.
Individuals with IGT are more susceptible to macrovascular disease (coronary artery, peripheral vascular, cerebrovascular), which often is present at the time of diagnosis.
Pharmacologic therapies and nonpharmacologic interventions such as weight reduction, improved diet, and increased physical activity may prevent the progression of IGT to type II diabetes by reducing insulin resistance.
Glucose intolerance that is first detected during pregnancy is classified as GDM. Excluded from this group are women who had diabetes before conception. GDM occurs in about 2% to 4% of pregnant women, usually during the second or third trimester, and is more common in women who are older, obese, or have a family history of diabetes.
This condition is important to identify because of the increased risk of fetal morbidity and mortality with GDM. Pregnant women should be screened with a 50-g, 1-hour glucose tolerance test during the 24th to 28th weeks of pregnancy.
Approximately 81% to 94% of women with GDM return to normal glucose tolerance after delivery.
However, women who have had GDM are at increased risk of developing type II diabetes, with approximately 30% to 40% developing type II diabetes or IGT within 10 to 20 years.
Problems With Classification
Sometimes it is difficult to distinguish between type I and type II diabetes. For example, younger type II patients who are thin and taking insulin may resemble type I patients. In addition, some patients display the characteristics of type II diabetes and are not susceptible to ketoacidosis, yet they are taking insulin.
These patients should not be classified as type I based solely on their insulin regimen, because they are taking insulin for glycemic control rather than as a life-sustaining therapy to prevent ketoacidosis and death.
Type II diabetes sometimes is found in children or adolescents, who usually are above their ideal body weight, as are most type II adults. One type of diabetes found in the pediatric population is called maturity-onset diabetes of the young (MODY) and is an example of an autosomal dominant form of inheritance of diabetes.
Age alone should not be considered the diagnostic variable in these patients; they should be classified as having type II and not type I diabetes.
Another classification problem that can occur involves older patients who develop ketosis-prone, type I diabetes. The onset of this form of diabetes is slower in older adults and may resemble type II diabetes for a considerable amount of time. These individuals tend to be at or slightly below their ideal weight and respond poorly to oral antidiabetic agents.
Ketones in their urine indicate a true lack of insulin. The insulin requirements thus become obvious and insulin therapy must be started to avoid severe ketoacidosis, coma, and death. These patients are more insulin sensitive than their obese counterparts with type II diabetes and require less insulin to control their diabetes.