The causes and symptoms of diabetes mellitus
Type 1 diabetes is usually caused by an abnormal reaction in which the immune system destroys insulin-secreting cells in the pancreas.
What are the causes of diabetes mellitus?
The cause of this reaction is unknown, but it may be triggered by a viral infection. In some cases, destruction of insulin-secreting tissues occurs following inflammation of the pancreas (see Acute pancreatitis). Genetics may also play a role, but the pattern of inheritance is complicated. A child of a person with type 1 diabetes is at greater risk of developing the same type of diabetes, but most affected children do not have a parent with diabetes. The causes of type 2 diabetes are less well understood, but genetics and obesity are important factors. About 1 in 3 affected people has a relative with the same type of diabetes. Type 2 diabetes is a major health problem in affluent societies and a growing problem in some developing countries. As food intake increases, more people become overweight and the prevalence of the condition rises. In people who are predisposed to diabetes, the condition can be triggered by corticosteroid drugs or by excessively high levels of natural corticosteroid hormones (see Cushing's syndrome), which act against insulin.
What are the symptoms of diabetes mellitus?
Although some of the symptoms of both forms of diabetes mellitus are similar, type 1 diabetes tends to develop more quickly and become more severe. The symptoms of type 2 may not be obvious and may go unnoticed until a routine medical checkup. The main symptoms of both forms may include:
- Excessive passing of urine.
- Thirst and a dry mouth.
- Insufficient sleep because of the need to pass urine at night.
- Lack of energy.
- Blurred vision.
Type 1 diabetes may also cause weight loss. In some people, the first sign of the disorder is ketoacidosis, a condition in which toxic chemicals called ketones build up in the blood. These chemicals are produced when the tissues of the body are unable to absorb glucose from the bloodstream, due to inadequate production of insulin, and have to use fats for energy. Ketoacidosis can also occur in people with type 1 diabetes who are taking insulin if they miss several doses or if they develop another illness (because any form of illness increases the body's requirement for insulin). The symptoms of ketoacidosis may include:
- Nausea and vomiting, sometimes with abdominal pain.
- Deep breathing.
- Acetone smell to the breath (like nailpolish remover).
The development of these symptoms is a medical emergency because they can lead to severe dehydration and coma if they are not treated urgently. Emergency treatment for ketoacidosis includes intravenous infusion of fluids to correct dehydration and restore the chemical balance of the blood, and injections of insulin to enable body cells to absorb glucose from the blood.
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