»   About Diabetes Mellitus   »   Types of Diabetes

Types of Diabetes

Types of DiabetesMost people know two main types of diabetes mellitus – type 1 diabetes (insulin-dependent) and type 2 diabetes (non-insulin-dependent). In fact, there are much more types of this disease, some of which can be interconnected. Whatever type of diabetes is diagnosed, the most important thing is to understand the reasons of hyperglycaemia in order to treat in efficiently. The following is the aetiological classification of diabetes mellitus:

Type 1 diabetes:

  • Autoimmune diabetes
  • Idiopathic diabetes

Type 2 diabetes:

  • In patients with normal weight
  • In overweight patients

Other types of diabetes caused by:

  • Genetic defects of pancreas β-cells
  • Genetic defects of insulin action
  • Diseases of the exocrine pancreas
  • Endocrinopathies
  • Drugs/chemicals
  • Infections
  • Uncommon forms of immune mediated diabetes
  • Certain genetic syndromes

Gestational diabetes

Type 1 Diabetes

Type 1 diabetes mellitus is characterized by the destruction of the pancreas β-cells, which leads to absolute insulin deficiency. It can also be referred to as insulin-dependent diabetes or juvenile diabetes (for more details, please read the “Juvenile Diabetes” Section).

Autoimmune diabetes occurs in 5-10% of all cases of diabetes. It develops due to the destruction of pancreas β-cells in the result of autoimmune reaction, which means that the body attacks its own cells and destroys them. The development of this type of diabetes is usually rapid in infants and children, and slow in adults. Most often, it occurs in childhood and adolescence. Autoimmune diabetes has multiple genetic predispositions. What is more, it may trigger other autoimmune disorders.

Idiopathic diabetes refers to type 1 diabetes mellitus of unknown aetiology. People with such type of diabetes have permanent insulinopenia (deficient production of insulin) and sometimes ketoacidosis while having no signs of autoimmune reactions. Most people with idiopathic diabetes are of Asian or African ancestry. Idiopathic type 1 diabetes is strongly inherited.

Type 2 Diabetes

Type 2 diabetes mellitus is characterized by the lack of response on insulin (insulin resistance) with relative insulin deficiency or by the defect of insulin secretion with insulin resistance. It can also be referred to as non-insulin dependent diabetes or adult-onset diabetes. The causes of type 2 diabetes are different from type 1 diabetes (for more details, please read the “Causes of Diabetes” Section). This is the prevalent type of diabetes mellitus making 85-90% of all cases of diabetes.

The biggest part of type 2 diabetes patients is overweight. Excessive weight and obesity is to some degree a reason of insulin resistance. In this case, healthy diet and weight loss may somewhat help to keep control over diabetes and normalize the carbohydrate metabolism.

More rarely, type 2 diabetes occurs in patients with normal weight. While their weight may be at a normal range, the body fat percentage may be increased, which also caused insulin resistance.

This type of diabetes may take many years to become noticeable, as it develops gradually. It is rarely accompanied by ketoacidosis. Patients with type 2 diabetes are often at risk of microvascular and cardiovascular complications. Type 2 diabetes is characterized by a much stronger genetic predisposition than type 1 diabetes.

Other Types of Diabetes

Diabetes caused by genetic defects of the pancreas β-cells usually occur at an early age. This type of diabetes is also referred to as maturity-onset diabetes of the young (MODY). It is characterized by the impaired insulin secretion by the β-cells. Insulin action is usually normal or has minor defects. Genetic abnormalities of this type prevent the human body convert proinsulin into insulin.

Diabetes associated with genetic defects in insulin action is caused by the mutations of the insulin receptor. This condition does not always lead to severe diabetes and may cause hyperinsulinemia or moderate hyperglycaemia. It prevents insulin from performing its function, which immediately leads to increased blood sugar levels.

Diabetes caused by exocrine pancreas diseases is explain by the reduction of the β-cell number, which leads to insufficient production if insulin. These diseases include pancreatitis, trauma, pancreatectomy, pancreatic carcinoma (cancer). Besides, pancreas β-cells may be damaged by extensive cystic fibrosis, haemochromatosis, and fibrocalculous pancreatopathy.

Diabetes is associated with those endocrinopathies that are characterized by excessive production of those hormones that antagonize the action of insulin. Such hormones include the growth hormone, glucagon, cortisol, and epinephrine. Respectively, acromegaly, glucagonoma, Cushing’s syndrome, and phaeochromocytoma can become the cause of diabetes mellitus. When the release of the above listed hormones is normalized, hyperglycaemia usually resolves as well. Partly, diabetes can be induced by somatostatinoma- and aldosteronoma-induced hypokalemia.

Very rarely, diabetes can develop as a result of drug therapy in some patients. The inducers are glucocorticoids, thyroid hormone, and β-adrenergic agonists. They may impair the action of insulin to a certain extent. As a rule, these drugs trigger diabetes mellitus in patients already having a certain level of insulin resistance. Concerning toxins, rat poison Vacor and intravenous pentamidine are known to destroy the pancreas β-cells, which causes insulin deficiency.

Certain infections may lead to the destruction of pancreas β-cells, which is the reason of permanent insulin deficiency and thus diabetes. These infections include coxsackie virus B, adenovirus, cytomegalovirus, and mumps. These infections trigger diabetes only in a certain number of cases. This list can be complemented with congenital rubella. It should be noted that diabetes develops in patients with this infection when they also have HLA (human leukocyte associated antigen) and other signs of type 1 diabetes.

Uncommon forms of immune-mediated diabetes are caused by stiff-syndrome and anti-insulin receptor antibodies. In the first case, it is known that about one third of patients suffering from the stiff-syndrome develop diabetes. In the second case, anti-insulin receptor antibodies that cause hyperglycaemia can be found in patients with autoimmune diseases, especially systemic lupus erythematosus. Nevertheless, these antibodies do not always act as insulin antagonists, and thus may also cause hypoglycaemia.

Certain genetic syndromes like Down’s syndrome, Klinefelter’s syndrome, Turner’s syndrome are often accompanied by the development of diabetes. Additionally, diabetes is a common condition for those suffering from Wolfram’s syndrome.

Gestational Diabetes Mellitus (GDM)

Gestational diabetes mellitus is the condition that is characterized by glucose intolerance that occurred or was first noticed during pregnancy. This condition most often happens in the 3rd trimester. GDM may either resolve after delivery, or remain developing into type 2 diabetes mellitus. It may be managed either by insulin or diet treatment. (For more details, please read the “Gestational Diabetes”).

See also: