There are two major types of diabetes, called type 1 and
type 2. Type 1 diabetes was also formerly called insulin dependent diabetes mellitus
(IDDM), or juvenile onset diabetes mellitus. In type 1 diabetes, the pancreas
undergoes an autoimmune attack by the body itself, and is rendered incapable of
making insulin. Abnormal antibodies have been found in the majority of patients
with type 1 diabetes. Antibodies are proteins in the blood that are part of the
body's immune system. The patient with type 1 diabetes must rely on insulin
medication for survival.
In autoimmune diseases, such as type 1 diabetes, the immune system mistakenly manufactures antibodies and inflammatory cells that are directed against and cause damage to patients' own body tissues. In persons with type 1 diabetes, the beta cells of the pancreas, which are responsible for insulin production, are attacked by the misdirected immune system. It is believed that the tendency to develop abnormal antibodies in type 1 diabetes is, in part, genetically inherited, though the details are not fully understood.
Exposure to certain viral infections (mumps and Coxsackie viruses) or other environmental toxins may serve to trigger abnormal antibody responses that cause damage to the pancreas cells where insulin is made. Some of the antibodies seen in type 1 diabetes include anti-islet cell antibodies, anti-insulin antibodies and anti-glutamic decarboxylase antibodies. These antibodies can be detected in the majority of patients, and may help determine which individuals are at risk for developing type 1 diabetes.
At present, the American Diabetes Association does not recommend general screening of the population for type 1 diabetes, though screening of high risk individuals, such as those with a first degree relative (sibling or parent) with type 1 diabetes should be encouraged. Type 1 diabetes tends to occur in young, lean individuals, usually before 30 years of age, however, older patients do present with this form of diabetes on occasion. This subgroup is referred to as latent autoimmune diabetes in adults (LADA). LADA is a slow, progressive form of type 1 diabetes. Of all the people with diabetes, only approximately 10% have type 1 diabetes and the remaining 90% have type 2 diabetes.
Type 2 diabetes was also previously referred to as non-insulin
dependent diabetes mellitus (NIDDM), or adult onset diabetes mellitus (AODM). In
type 2 diabetes, patients can still produce insulin, but do so relatively
inadequately for their body's needs, particularly in the face of insulin
resistance as discussed above. In many cases this actually means the pancreas
produces larger than normal quantities of insulin. A major feature of type 2
diabetes is a lack of sensitivity to insulin by the cells of the body (particularly fat and muscle
cells).
In addition to the problems with an increase in insulin resistance, the release of insulin by the pancreas may also be defective and suboptimal. In fact, there is a known steady decline in beta cell production of insulin in type 2 diabetes that contributes to worsening glucose control. (This is a major factor for many patients with type 2 diabetes who ultimately require insulin therapy.) Finally, the liver in these patients continues to produce glucose through a process called gluconeogenesis despite elevated glucose levels. The control of gluconeogenesis becomes compromised.
While it is said that type 2 diabetes occurs mostly in individuals over 30 years old and the incidence increases with age, we are seeing an alarming number patients with type 2 diabetes who are barely in their teen years. Most of these cases are a direct result of poor eating habits, higher body weight, and lack of exercise.
While there is a strong genetic component to developing this form of diabetes, there are other risk factors - the most significant of which is obesity. There is a direct relationship between the degree of obesity and the risk of developing type 2 diabetes, and this holds true in children as well as adults. It is estimated that the chance to develop diabetes doubles for every 20% increase over desirable body weight.
Regarding age, data shows that for each decade after 40 years of age regardless of weight there is an increase in incidence of diabetes. The prevalence of diabetes in persons 65 years of age and older is around 27%. Type 2 diabetes is also more common in certain ethnic groups. Compared with a 7% prevalence in non-Hispanic Caucasians, the prevalence in Asian Americans is estimated to be 8%, in Hispanics 12%, in blacks around 13%, and in certain Native American communities 20% to 50%. Finally, diabetes occurs much more frequently in women with a prior history of diabetes that develops during pregnancy (gestational diabetes).
Diabetes can occur temporarily during pregnancy, and reports suggest that it
occurs in 2% to 10% of all pregnancies. Significant hormonal changes
during pregnancy can lead to blood sugar elevation in genetically predisposed
individuals. Blood sugar elevation during pregnancy is called
gestational
diabetes. Gestational diabetes usually resolves once the baby is born. However,
35% to 60% of women with gestational diabetes will eventually develop type 2
diabetes over the next 10 to 20 years, especially in those who require insulin during pregnancy
and those who remain overweight after their
delivery. Patients with gestational diabetes are usually asked to undergo an
oral glucose tolerance test about
six weeks after giving birth to determine if
their diabetes has persisted beyond the pregnancy, or if any evidence (such as
impaired glucose tolerance) is present that may be a clue to the patient's
future risk for developing diabetes.
"Secondary" diabetes refers to elevated blood sugar levels from another medical condition. Secondary diabetes may develop when the pancreatic tissue responsible for the production of insulin is destroyed by disease, such as chronic pancreatitis (inflammation of the pancreas by toxins like excessive alcohol), trauma, or surgical removal of the pancreas.
Diabetes can also result from other hormonal disturbances, such as excessive growth hormone production (acromegaly) and Cushing's syndrome. In acromegaly, a pituitary gland tumor at the base of the brain causes excessive production of growth hormone, leading to hyperglycemia. In Cushing's syndrome, the adrenal glands produce an excess of cortisol, which promotes blood sugar elevation.
In addition, certain medications may worsen diabetes control, or "unmask" latent diabetes. This is seen most commonly when steroid medications (such as prednisone) are taken and also with medications used in the treatment of HIV infection (AIDS).
In autoimmune diseases, such as type 1 diabetes, the immune system mistakenly manufactures antibodies and inflammatory cells that are directed against and cause damage to patients' own body tissues. In persons with type 1 diabetes, the beta cells of the pancreas, which are responsible for insulin production, are attacked by the misdirected immune system. It is believed that the tendency to develop abnormal antibodies in type 1 diabetes is, in part, genetically inherited, though the details are not fully understood.
Exposure to certain viral infections (mumps and Coxsackie viruses) or other environmental toxins may serve to trigger abnormal antibody responses that cause damage to the pancreas cells where insulin is made. Some of the antibodies seen in type 1 diabetes include anti-islet cell antibodies, anti-insulin antibodies and anti-glutamic decarboxylase antibodies. These antibodies can be detected in the majority of patients, and may help determine which individuals are at risk for developing type 1 diabetes.
At present, the American Diabetes Association does not recommend general screening of the population for type 1 diabetes, though screening of high risk individuals, such as those with a first degree relative (sibling or parent) with type 1 diabetes should be encouraged. Type 1 diabetes tends to occur in young, lean individuals, usually before 30 years of age, however, older patients do present with this form of diabetes on occasion. This subgroup is referred to as latent autoimmune diabetes in adults (LADA). LADA is a slow, progressive form of type 1 diabetes. Of all the people with diabetes, only approximately 10% have type 1 diabetes and the remaining 90% have type 2 diabetes.
Type 2 diabetes
In addition to the problems with an increase in insulin resistance, the release of insulin by the pancreas may also be defective and suboptimal. In fact, there is a known steady decline in beta cell production of insulin in type 2 diabetes that contributes to worsening glucose control. (This is a major factor for many patients with type 2 diabetes who ultimately require insulin therapy.) Finally, the liver in these patients continues to produce glucose through a process called gluconeogenesis despite elevated glucose levels. The control of gluconeogenesis becomes compromised.
While it is said that type 2 diabetes occurs mostly in individuals over 30 years old and the incidence increases with age, we are seeing an alarming number patients with type 2 diabetes who are barely in their teen years. Most of these cases are a direct result of poor eating habits, higher body weight, and lack of exercise.
While there is a strong genetic component to developing this form of diabetes, there are other risk factors - the most significant of which is obesity. There is a direct relationship between the degree of obesity and the risk of developing type 2 diabetes, and this holds true in children as well as adults. It is estimated that the chance to develop diabetes doubles for every 20% increase over desirable body weight.
Regarding age, data shows that for each decade after 40 years of age regardless of weight there is an increase in incidence of diabetes. The prevalence of diabetes in persons 65 years of age and older is around 27%. Type 2 diabetes is also more common in certain ethnic groups. Compared with a 7% prevalence in non-Hispanic Caucasians, the prevalence in Asian Americans is estimated to be 8%, in Hispanics 12%, in blacks around 13%, and in certain Native American communities 20% to 50%. Finally, diabetes occurs much more frequently in women with a prior history of diabetes that develops during pregnancy (gestational diabetes).
Other types of diabetes
"Secondary" diabetes refers to elevated blood sugar levels from another medical condition. Secondary diabetes may develop when the pancreatic tissue responsible for the production of insulin is destroyed by disease, such as chronic pancreatitis (inflammation of the pancreas by toxins like excessive alcohol), trauma, or surgical removal of the pancreas.
Diabetes can also result from other hormonal disturbances, such as excessive growth hormone production (acromegaly) and Cushing's syndrome. In acromegaly, a pituitary gland tumor at the base of the brain causes excessive production of growth hormone, leading to hyperglycemia. In Cushing's syndrome, the adrenal glands produce an excess of cortisol, which promotes blood sugar elevation.
In addition, certain medications may worsen diabetes control, or "unmask" latent diabetes. This is seen most commonly when steroid medications (such as prednisone) are taken and also with medications used in the treatment of HIV infection (AIDS).
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