What is MODY?
MODY refers to a rare form of diabetes which differs from the more common Type 1 and 2 diabetes mellitus and its runs in families. It is caused by a mutation in one of the genes of the individual and it’s this mutation that is inherited. Either of a person’s parents must have the MODY gene in order for an individual to have it. Children borne to parents with the MODY gene have a 50% chance of inheriting the gene and developing MODY too.
Currently, there are 12 different forms of MODY with each having distinct characteristics, symptoms and treatment methods, but only 3 are most common. MODY 1 and 3 affect the ability of the β-cells of the pancreas to secrete insulin in response to rising meal-time blood sugar levels. MODY 2 on the other hand affects the body’s thermostat used to regulate fasting blood sugar, causing them to remain higher than normal at all times, even though meal-time insulin secretions remain normal.
MODY affects up to 5% of people with diabetes mellitus. A distinctive feature of people with MODY is they are underweight and about 20% of people diagnosed with Type 2 diabetes mellitus are not overweight, which emphasizes the need for detection of the MODY gene in these individuals.
This disorder is quite similar to type 1 than type 2 albeit, it tends to be confused with either type.
Distinguishing MODY from Type 1 and 2 diabetes mellitus
- type 2 diabetes mellitus is caused by a defect in many genes, MODY is as a result of defect in just one gene.
- type 2 diabetes mellitus is usually associated with being overweight or obese but this is not always the case with MODY or Type 1 diabetes mellitus.
- in as much as distinguishing MODY from Type 2 diabetes mellitus based on family history can be hard, 2 or more consecutive generations of diabetes (with young onset in at least one family member) and the absence of significant obesity or insulin resistance is most suggestive of MODY.
How do I diagnose MODY?
The first step in diagnosing MODY is having a blood sugar test. Having done this, your doctor will have to figure out if you have MODY or another type of diabetes mellitus.
Blood tests normally can help determine which type of diabetes mellitus a person has but with MODY the case is quite different. In type 1 diabetes, antibodies attack the pancreas but in MODY, there are no antibody actions. With respect to insulin resistance, it is not present in non-obese people with MODY, but it occurs in obese people with MODY.
Unfortunately, the surest way to diagnose MODY is to take a total of 6 diagnostic tests which are quite expensive. The type of testing will determine the exact type of MODY, if there is a mutation in one of the MODY genes, then type 1 and 2 diabetes mellitus can be ruled out.
The 6 MODY genes include:
- HNF1α – mutation causes about 70% of MODY cases
Factors that may suggest you have MODY.
Please note that the following factors aren’t absolute and so therefore, what these do is to make testing for MODY worth the while, considering its expensive nature.
- If you are diagnosed with diabetes though you have always been of a normal or near normal weight or were at a normal weight until shortly before your diabetes diagnosis.
- If as a female, you have a history of gestational diabetes that occurred when you were at a normal weight and developed early in the course of the pregnancy. Please note the difference here is, gestational diabetes without MODY gene occurs within the 6th and 7th month of pregnancy while in those with the MODY gene, it occurs in the early stages of pregnancy.
- If you have close relatives who has adult onset diabetes but were of normal weight.
- If taking a drug to improve insulin resistance for example metformin, doesn’t make significant changes to your HbA1c and you have no evidence of autoimmune diabetes (Type 1 diabetes)
- If you have very high fasting blood sugar that is not lowered by diet, drug or insulin.
- If you have several relatives with both type 1 and 2 diabetes but none are obese.
Symptoms of MODY
Similar to type 2 diabetes but different from type 1, symptoms of MODY tend to develop slowly. Early symptoms include blurry vision, recurrent skin infections, frequent urinations, increased thirst and decreased weight.
Treatment of MODY
Due to the varying effects of the MODY sub-types, treatment methods tend to differ. For MODY 1,3 and 4, drugs of the oral sulphonylurea class are usually effective. These include glipizide, glyburide etc. MODY 2 is usually resolved using exercise and diet and rarely requires drug or insulin therapy.
Note: people with MODY normally respond to very low doses of sulphonylureas. So, this can also serve as a differential diagnosis for people with or without MODY. Insulin used to treat MODY is usually required in very small doses, as low as 10-20 units depending on the body size.