Diabetes | Causes of diabetes

Diabetes is metabolic alteration resulting from a decline in insulin activity. In particular, diabetes may be due to a reduced availability of this hormone to an impediment to its normal action, or a combination of these two factors. A feature always present in diabetes mellitus is the ' hyperglycemia, which with the passage of time, tend to associate certain complications of blood vessels: the macro vascular (ie a ' atherosclerosis particularly severe and early),that is not specific of diabetes, and  macroangiopathy (ie changes in the movement of small arteries, which become particularly apparent in the retina, the kidney and nerve), which is specific to the disease.

Diabetes mellitus is a common disease. In the United States are reported each year about 200,000 new cases of diabetes mellitus and the percentage of world population affected by the disease is estimated at 5%, with a slightly higher prevalence in women (approximately 25% more than males). The prevalence of diabetes mellitus in Italy is 3%. It increases with age ranging from 0.5% in the age group under 30 years up to 10% or more above the age of 65. About 90% of the diabetic population suffers from type 2 diabetes, while only a minority suffers from type 1 diabetes.

Diabetes and impaired glucose tolerance

By definition, diabetes is characterized by hyperglycemia. To determine this, and then to see whether or not there is diabetes, perform a venous blood sample (as used in most laboratories), and on it, you go to determine what is the amount of glucose present.

Under the new criteria proposed by the expert committee of the ADA (1997), to say that a person is suffering from diabetes, they must satisfy the following criteria:

    - When blood sugar is > 200 milligrams of glucose on deciliter of blood ( mg / dl ) at any time of day;

    - When the fasting blood glucose > 126 mg / dl;

    - When your blood sugar level after 120 minutes from ' OGTT ( oral glucose tolerance test ) is > 200 mg / dl.

The ADA and the WHO use the term impaired glucose tolerance ( IGT, Impaired Glucose Tolerance ) to indicate a metabolic state intermediate between normal and diabetes, in which blood glucose is determined two hours after oral glucose load and must be between 140 and 200 mg / dl.

Classification

The classification accepted by the WHO in 1980 provided for the division into five classes of diabetes. According to this classification are distinguished:

    - Diabetes , "insulin-dependent (IDDM)" , as defined above also infant-juvenile diabetes;

    - Diabetes is a  "non-insulin dependent (NIDDM) , also known as diabetes of ' adulthood or maturity;

    - Diabetes from malnutrition , especially common in tropical countries;

    - other types of diabetes secondary to other diseases such as pancreatic disease ( chronic pancreatitis , pancreatic cancer ), endocrine diseases responsible for an excessive secretion of counterregulatory hormones ( Cushing's syndrome , acromegaly ,  pheochromocytoma , hyperthyroidism , Glucagonom, somatostatinoma, aldosteronoma); use of drugs that induce hyperglycemia (glucocorticoids, thyroid hormone , interferon, pentamidine, adrenergic agonists); intake of toxic substances abnormalities of insulin or its receptor, genetic abnormalities;

    - A gestational diabetes ( GDM ) , linked to pregnancy .

A new classification, the easier and now internationally recognized, dividing it in type 1 diabetes, accounted for almost all of the immune form (ie, mediated by a dysregulation of the immune system of the subject), and type 2 diabetes, should instead to a deficiency of insulin secretion by pancreatic cells or tissue resistance to the status of the action of insulin itself. Any form of diabetes may require insulin therapy at any stage it is found, therefore the use of insulin in itself does not classify the patient. It is therefore wrong to classify the various forms of insulin-dependent diabetes and insulin-independent.

Other much more rare forms may be associated with viral infections (congenital rubella, cytomegalovirus), a common form of diabetes is not mediated by the immune system to various genetic syndromes (Down, Klinefelter, Turner, Friedreich's ataxia, Laurence Moon Biedl syndrome, myotonic dystrophy , Prader Willi syndrome, Huntington's disease) or to particular conditions of insulin resistance. This category of rare forms of diabetes also caused a clearly identified genetic defects in hereditary nature of the cell, usually arising at a young age, characterized by modest hyperglycemia and defined - for their similarity with the clinical type 2 diabetes - MODY, or Maturity Onset Diabetes of the Young.