Canadian Health and Care Mall – What is Diabetes?

CAUSES OF DIABETES

Inheritance

CAUSES OF DIABETES

Several members of my family developed diabetes when we were young and most of us are controlled by tablets. I’ve been told we are a MODY family. What does this mean?

MODY stands for Maturity-Onset Diabetes of the Young. (Maturity-onset diabetes is an earlier name for Type 2 diabetes.) In the 1970s, it was noticed that a handful of families seemed to develop diabetes in their teens or twenties and about 50% of family members were affected. This suggests a certain sort of inheritance (autosomal dominant); those family members with diabetes have a specific defect in their insulin-producing cells. Research into these patients has increased our understanding of the causes of diabetes. There are several distinct types of MODY, but generally people in this group can control their diabetes with tablets and do not usually need insulin.

If diabetes is known to be in my family, should I or my children take any preventive action?

The inheritance of diabetes is a complicated subject and different types of diabetes are inherited in different ways. In Type 1 diabetes some family members may carry an increased risk, which can be identified by genetic testing.

However, only a small proportion of the people who inherit this risk will go on to develop diabetes and no one has been able to pin down the factors that cause this to happen.

Type 2 diabetes is more strongly inherited than Type 1, and therefore often affects several members of the same family. It is now clear that a number of different genes are involved. The picture which is slowly emerging suggests that there are several different forms of Type 2 diabetes. The genetics of one rare form of inherited diabetes, called MODY, have been investigated in great detail and have increased our understanding of this condition but these discoveries do not apply to the vast majority of people with Type 2 diabetes (see MODY question above).

There is now evidence that family members who are at risk may put off developing diabetes by regular exercise, losing weight and sometimes by taking medication. They should have a blood glucose test as soon as they develop any relevant symptoms, so that diabetes can be detected and treated early.

I am 16 and have had diabetes for five years. Why has my identical twin brother not got diabetes?

A large 20-year research project has studied examples of identical twins with diabetes. The results show a difference between the way Type 1 and Type 2 diabetes are inherited. If you have an identical twin with Type 1 diabetes, you have only a 50% chance of developing diabetes yourself. On the other hand, if you had Type 2 diabetes (extremely unusual at the age of 11) your twin would be almost certain to get the same sort of diabetes. If your twin brother has not developed diabetes within the last five years, he has a very low risk of developing the condition.

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