Diabetes Mellitus

Diabetes, better known as diabetes mellitus, is one of the most metabolic disease that can affect the human being.
It relates its onset to insulin; it may depend on a reduced availability of insulin (whose production does not meet the body’s needs), on the low sensitivity to the hormone by the target tissues or, finally, on a combination of these factors.

A clinical feature of diabetes is hyperglycaemia, resulting from the aforementioned changes to insulin.
The medical-scientific community recognises the existence of 3 major types of diabetes mellitus, which are: type 1 diabetes, type 2 diabetes and gestational diabetes; at one time, the classification of diabetes was broader and less simple to consult.

The presence of diabetes in the world population is increasing in the last 30-40 years: consider that, while in 1980 the patients were 108 million, in 2014 the number of people with diabetes reached 422 million.

What is Diabetes Mellitus?

Diabetes mellitus, or diabetes, is a metabolic disease resulting from a decline in insulin activity, a hormone produced by the beta cells of the islets of Langerhans of the pancreas.
In particular, diabetes may be caused by:

• Reduced insulin availability – To understand: there is less insulin than the body would need for its proper functioning;
• An impediment to the normal action of insulin – To understand: insulin is present, but the body cannot well use it;
• A combination of the two aforementioned factors – To understand: insulin is low and does not work properly.
• A feature always present in diabetes mellitus is hyperglycaemia (high concentration of glucose in the blood), which, over time, is associated with vascular complications, such as:
• macroangiopathy (a severe and early form of atherosclerosis)
  microangiopathy (an alteration of the blood circulation inside the small arterial vessels, manifested mainly in the retina, kidney and nerves).

While microangiopathy is specific to the disease in question, macroangiopathy is not.

Diabetes Types

There are various types of diabetes mellitus and it is for this reason that the medical community has always tried to draw up a classification that was as reliable, complete and above all easy to consult, even by the less experienced.

Among the various classifications of diabetes proposed over the last few decades, two are reported: one dating back to 1980, drawn up by the WHO (World Health Organization) in force until 1997, and one dating back to 1997, planned by the WHO and from the ADA (American Diabetes Association, in English, and the American Diabetes Association, in Italian) to replace the one just named and still in force today.

THE “OLD” CLASSIFICATION

The classification proposed by the WHO in 1980 foresees the division of diabetes mellitus into five different classes, identified as:

• Insulin-dependent diabetes, also defined by the acronym IDDM or infant-juvenile diabetes;
• Non-insulin-dependent diabetes, also defined by the acronym NIDDM or diabetes of adulthood or maturity;
• Malnutrition diabetes. This was the name of the widespread diabetes in tropical countries;
• Gestational diabetes or GDM. It took this name from diabetes linked to pregnancy;
• Other types of diabetes. With this statement, the experts referred to forms of diabetes mellitus secondary to: pathologies, including:
  • pancreatic diseases (chronic pancreatitis and pancreatic cancer),
  • endocrine disorders responsible for excessive secretion of interangular insulin hormones (Cushing’s syndrome, acromegaly, pheochromocytoma, hyperthyroidism, glucagon, somatostatin and aldosterone)
  • using drugs that induce hyperglycaemia (glucocorticoids, thyroid hormones, interferon, pentamidine and adrenergic agonists)
  • the intake of toxic substances;
  • the abnormalities of insulin or its receptor;
  • specific genetic abnormalities.

THE “NEW” CLASSIFICATION

Internationally recognised, the classification of diabetes mellitus drawn up in 1997 by the WHO and ADA is decidedly simpler than the previous one. In fact, it divides diabetes into three main types:

• Type 1 diabetes mellitus: This includes most of the immune-mediated diabetic forms; in these circumstances, the underlying cause is a malfunction of the immune system, which, recognising the pancreatic beta cells of the Langerhans islands as foreign, attacks them and destroys them.
  Since it implicates the immune system, type 1 diabetes mellitus is rightfully among the autoimmune diseases.
• Type 2 diabetes mellitus: This includes all forms of diabetes:
  • ?A deficiency of insulin secretion, by pancreatic beta cells of the islets of Langerhans,
  • Resistance of the body’s tissues to the action of insulin (a condition known as insulin resistance).
• Gestational diabetes: As it was in the old classification, this includes the forms of diabetes secondary to the state of pregnancy. It is a transient phenomenon.

It should be noted that the types “type 1 diabetes” and “type 2 diabetes” also include the diabetic forms associated with: viral infections (eg rubella, cytomegalovirus), genetic syndromes (Down syndrome, Klinefelter syndrome, Turner syndrome , Friedreich’s ataxia, Laurence-Moon syndrome, myotonic dystrophy, Prader-Willi syndrome, Huntington’s chorea, etc.) and hereditary genetic defects of pancreatic beta cells in the Langerhans islands (known as MODY, or Maturity-Onset Diabetes of the Young).

Epidemiology

Diabetes mellitus is a common disease; among the metabolic diseases, it is certainly the most known and probably also the most widespread.
According to WHO reports, in 2014, the prevalence of diabetes among adults around the world over the age of 18 was 8.5% and the number of individuals with diabetes mellitus in the population of all the world was 422 million.

Comparing these statistical results with those of 1980, a disturbing difference emerges: 34 years earlier, the prevalence on the same category of people was 4.7%, while the number of sick people worldwide was only 108 million. Therefore, from 1980 to 2014, the prevalence almost doubled and the number of sick individuals has quadrupled.

Between type 1 diabetes mellitus and type 2 diabetes mellitus, the latter is decidedly more widespread than the first: according to most estimates, about 90% of the diabetic population suffers from type 2 diabetes and only the remaining 10% carries type 1 diabetes.

As far as gestational diabetes is concerned, the most reliable estimates say that this diabetic form affects 8% of the female population.

Stats

Statistical data and interesting numbers related to diabetes mellitus:

• The prevalence of diabetes mellitus increases with age and, in Italy, reaches its peak in the population aged around 70-75 years.
• People in a state of impaired fasting glucose (IGF) have a 50% chance of developing type 2 diabetes mellitus over the 10 years following the diagnosis of IGF.
• According to the WHO, in 2012, around 1.5 million people worldwide died directly from diabetes mellitus.
• Worldwide, about half of all deaths from diabetes mellitus involve people around 70 years old. According to WHO estimates, diabetes will be the 7th leading cause of death in the general population in 2030.
• ?In 2008-2009, the annual incidence of diabetes in young people measured 18,436 cases, with regard to type 1 diabetes, and 5,089 cases, as regards type 2 diabetes.
• 90% of diabetes cases are type 2 diabetes, while the remaining 10% are type 1 diabetes.

Pre-Diabetes

Pre-diabetes: what it is and how to distinguish it from diabetes mellitus. Hints of diagnosis.

As mentioned, by definition, diabetes mellitus is characterised by hyperglycaemia.
To determine hyperglycaemia – and to determine whether there is diabetes – a venous blood sample is taken and the subsequent measurement, on this blood sample, of the amount of glucose present.
According to the latest criteria proposed by the ADA experts, a person suffers from diabetes when there are the following three conditions:

• Blood glucose (ie blood glucose concentration) is  200 milligrams of glucose per decilitre of blood (mg / dl) at any time of the day.
• Fasting blood glucose is  126 mg / dl.
• In normal conditions it should be less than 100 mg / dl.
• Blood glucose after 120 minutes from the OGTT (oral glucose tolerance test or oral glucose loading test) is ? 200 mg / dl.
• In normal conditions it should be less than 140 mg / dl.

Pre-diabetes is a condition that often precedes the onset of type 2 diabetes mellitus, therefore its identification must sound like an alarm bell.
Those suffering from prediabetes do not have the same symptomatology as the diabetes patient and often do not even have a symptom of the latter; nevertheless, like the diabetic subject, it presents abnormal blood glucose levels, higher than normal.
According to the ADA and the WHO, there are two subtypes of prediabetes: the subtype called impaired fasting glucose or IGF and the subtype called impaired glucose tolerance or IGT.

Altered fasting blood glucose

To diagnose impaired fasting blood glucose, glucose levels higher than normal, but not high enough to be in a state of diabetes, must be detected after at least 8 hours of fasting.

Altered glucose tolerance

On the contrary, to diagnose impaired glucose tolerance, it is necessary that the glycaemia, after the so-called oral glucose tolerance test, is between 140 and 200 mg / dl (in substance it is above the normal threshold, but lower than the limit that establishes the presence of diabetes).