Why does diabetes mellitus occurs?

Hi, there. My neighbor was at the doctor yesterday and she is suspected to have diabetes mellitus. She will have to go to more test to verify it. I am interested in why diabetes mellitus occurs. What are the causes of this disease? I would really appreciate if someone could answer me that.

Hello. There are two main types of diabetes – type 1 and type 2. They have different causes. No one knows for sure why type 1 appears, but some facts are known. Predisposition in family is much stronger with type 2 than with this type. For this disease, it is believed to be autoimmune. There is a lack of endocrine cells that produce insulin with this type of diabetes. Some scientists connect that with certain viral infections. Body’s immune system reacts to these cells and destroys them. There is a lack of insulin in organism and in that way glucose cannot enter the cell for energy purposes. In type 2 there is a normal number of cells that produce insulin. However, there is a lack of receptors for insulin on target cells. In some cases, the amount of insulin is normal, but the molecule itself is inefficient.