Diabetes mellitus is a chronic metabolic disorder that affects the body's energy processes. After daily food intake, a significant portion of nutrients is broken down into sugars (glucose), which are then transported into the bloodstream. When blood sugar levels (glycemia) exceed a certain threshold, the pancreas kicks in. It releases the hormone insulin, the most important metabolic key in the entire energy process. The precise amount of glucose released into the bloodstream is controlled by this key hormone. In diabetic patients, the pancreas is unable to produce enough insulin to regulate these glucose levels, which tend to rise uncontrollably in the blood. This leads to damage to the nervous, renal, and cardiovascular systems, as well as adverse effects on vision.
It is important to know that diabetes is not contagious; living with someone who has diabetes will not cause you to contract it. It is not hereditary, meaning that, with the exception of a few very rare forms (such as MODY), there is no possibility of the disease being passed down from generation to generation. However, there is a familial predisposition, more pronounced in the case of type 2 diabetes, so those who have a first-degree relative (parents, siblings) with diabetes have a higher risk of developing the disease than those who have no relatives with the condition.
Diagnosis of diabetes
Diabetes is diagnosed in the following typical cases:
- Glycated hemoglobin (HbA1c) is greater than or equal to 6.5%.
- The blood glucose measured in the laboratory is equal to or greater than 126 mg/dl (in the morning, after 8 hours of fasting, in two circumstances).
- Blood glucose is equal to or greater than 200 mg/dl at the second hour after an oral glucose load (in two circumstances).
- Blood glucose is equal to or greater than 200 mg/dl at any time of day in the presence of disorders (symptoms) typical of the disease (one circumstance is sufficient).
There are also conditions in which blood glucose levels are suboptimal and represent an increased risk of developing diabetes in the future. These conditions are diagnosed and defined as follows:
- Glycated hemoglobin between 6.00 and 6.49% (high risk of diabetes)
- Fasting blood glucose between 100 and 125 mg/dl (altered fasting blood glucose)
- Blood glucose two hours after glucose ingestion between 140 and 199 mg/dl (glucose intolerance).
Approximately one in five people with these conditions will develop diabetes within 5 years.
Types of diabetes
Diabetes is a rather complex disease, as it encompasses multiple clinical syndromes. It can be considered a group of different diseases, united only by the fact that blood glucose levels are elevated.
The main types of diabetes are as follows:
- Type 1 diabetes (also called insulin-dependent diabetes) is of autoimmune origin and results from the relatively rapid destruction of the pancreatic cells that produce insulin. This destruction is caused by substances (antibodies, cytokines) produced by the body's immune system cells, probably in response to a virus or one or more toxins present in the environment.
- Type 2 diabetes (also called non-insulin-dependent diabetes) develops over several years due to a deficiency in insulin production. However, this deficiency is never as severe as that seen in type 1 diabetes and is not caused by autoimmunity. Multiple genetic alterations and acquired (environmental) factors are responsible for an insulin deficiency that is generally associated with reduced insulin effectiveness. Type 2 diabetes typically appears after the age of 40, but the age of onset is decreasing due to the increasing prevalence of obesity, even among younger people.
- Gestational diabetes develops during pregnancy and usually disappears after childbirth. Women who have had gestational diabetes are at risk of developing it again in subsequent pregnancies and type 2 diabetes later in life.
- Monogenic diabetes is a type characterized by a single genetic mutation that causes hyperglycemia. It is a hereditary form of diabetes (affecting a grandparent, parent, and child) and typically appears earlier than type 2 diabetes, although it shares many characteristics. A classic example is MODY (Maturity-Onset Diabetes of the Young), which has numerous variants depending on the gene involved. This category also includes the very rare neonatal diabetes mellitus and other equally rare variants.
- In secondary diabetes and drug-induced diabetes , other diseases or medications cause impaired insulin secretion or effectiveness. Diseases that can cause diabetes include chronic pancreatitis, liver cirrhosis, chronic kidney disease, acromegaly, and Cushing's syndrome. Diabetes can also develop when the pancreas is surgically removed. Diabetes, especially in predisposed individuals, can develop during prolonged treatment with corticosteroids or other medications.
As a collection of different diseases, each type of diabetes presents unique symptoms, causes, and treatments.
