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DiabeteshubDiabetesRarer types of diabetesMODY and other genetic reasons that cause diabetesMODY diabetes

MODY diabetes

In rare instances, the cause of diabetes may be genetic abnormality. In approximately 2% of diabetes cases, the condition is caused by a single genetic defect.

The mutation in a single gene, i.e. a genetic defect, can cause diabetes using different mechanisms. In roughly 2 percent of diabetes cases, the cause is a defect like that.

MODY is short for “maturity onset diabetes of the young”. The terms dates back to a time when the knowledge of genetic defects was not as comprehensive as now. Over a dozen genes are known to cause MODY diabetes.

MODY is a dominant inherited disease. If one of the parents has MODY, each child has a 50 percent chance of inheriting the MODY gene. In most cases, MODY-related genetic defects result in diabetes in childhood, adolescence or as a young adult. MODY diabetes may also be first diagnosed during pregnancy, or it may not be diagnosed before middle age.

Sometimes, a person may be diagnosed with MODY diabetes without either of the parents or any relatives having diabetes – in which case a new genetic defect has occurred.

Some genetic defects are linked to other conditions, for instance, mutations in the kidney tubule or main bile duct, genital abnormalities, gout, changes in the liver enzymes or sodium level, steatorrhea or learning difficulties.

The chance of MODY diabetes should be examined if:

  • The clinical picture of diabetes does not seem to fit either type 1 or type 2 diabetes

  • Someone in the family has MODY diabetes

  • A woman of normal weight is diagnosed with gestational diabetes

The type of diabetes is established on the basis of antibody tests, blood C-peptide tests and, commonly, glucose tolerance tests. The diagnosis is confirmed by a genetic test done using a sample of blood.

There are already more than a dozen genes known, mutation in which can cause MODY diabetes.

MODY2 or glucokinase diabetes is the most common type of MODY in Finland. Typical of it is that the blood sugar level is slightly high when fasting but it does not remain high after a meal. Due to a mutation in the gene of the glucokinase enzyme, the pancreatic beta cells do not start to produce insulin until the blood sugar level becomes higher than normal. In many cases, good dietary choices are sufficient for managing MODY2.

MODY3 or HNF-1α diabetes is the second most common type of MODY in Finland. The pancreas contains cells that produce insulin but they do not normally react to an increased blood sugar level. In time, the secretion of insulin will become too diminished and the blood sugar level will heavily increase, especially after a meal but, further on, also while fasting. Making good dietary choices and using meal-time tablets will usually suffice initially, but insulin is also often necessary. Many of the drugs used to treat type 2 diabetes may also be effective, but there are no studies done into the subject.

In the majority of MODY cases, the pancreatic beta cells are able to produce insulin but they do not sense an increase in the blood sugar level the way healthy cells do.

In some cases, dietary management is enough, while some people need meal-time tablets, which release insulin from the beta cells. However, some genetic defects include damage to the insulin-producing beta cells, in which case MDI therapy is required.

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Updated 30.9.2023

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