The Genetics of Diabetes

model of human insulinWhy me? How did I deserve this? Am I to blame? These are questions that many people ask when diagnosed with a serious condition or disease.

Unfortunately, there’s no clear-cut answer when it comes to diabetes. Unlike some traits, diabetes doesn’t seem to be inherited in a simple pattern, and there is a lot of misinformation out there about its causes. (Have you ever had to explain that diabetes doesn’t happen because someone ate too much sugar?)

It’s apparent, though, that some people are born more likely to develop diabetes than others. We know that type 1 and type 2 diabetes have different causes, but genetics plays an important role in both types. People with diabetes inherit a predisposition to the disease, then something in their environment triggers it.

Identical twins are proof that genes alone are not enough, however. Identical twins have identical genes; therefore, they should have the same genetic risk for a disease—right? Not necessarily. Research has found that if one identical twin has type 1 diabetes, the other twin will get the disease about 50 percent of the time. For type 2 diabetes, that risk rises to as much as 4 in 5. In both type 1 and type 2, identical twins have a much higher risk of both developing diabetes than non-identical (fraternal) twins, which further supports the fact that genetics is involved.

So what are the causes of type 1 diabetes? Again, we know that genetics is involved. We also know that it’s not just one gene responsible, but many different genes, each of which contributes only a small part of the risk. Scientists have identified a few genes responsible for type 1, but the majority of the genetic risk is still unidentified.

Because of the data about identical twins, we know that type 1 diabetes doesn’t arise solely from genetics. Researchers are eager to find out what environmental factors could also contribute to type 1. Potential triggers that have been studied include:

  • Differences in climate—Type 1 diabetes develops more often in winter than summer, and the rate of type 1 is higher in countries with cold climates.
  • Bacteria or viruses—Because type 1 is an autoimmune disease, scientists have speculated that an infectious agent, either bacteria or viruses, could cause it.
  • Early diet—Type 1 is less common in people who were breastfed and in those who first ate solid foods at later ages.

Identifying environmental triggers has proved very difficult, and so far no single factor has been found that is clearly responsible.

What about risk for children born to people with type 1 diabetes? The overall risk that a child born in the United States will develop type 1 is about 1 in 300 to 400. That risk increases if the child’s parents have type 1, to about 1 in 50 if the mother has diabetes and to 1 in 25 if the father has diabetes. The child’s risk appears to be higher if the parent developed diabetes before age 11.

And what about type 2 diabetes? As with type 1 diabetes, genetics plays a role in type 2. Similar to type 1, identical twins show a high rate of both developing diabetes, approaching 75 to 80 percent, with a lower but still high rate for non-identical twins.

Because the rate of type 2 diabetes is not the same in identical twins, environmental causes are clearly involved in the onset. The primary factors appear to be excess weight gain and a sedentary lifestyle, but other factors may also play a role, such as environmental pollutants and the type of bacteria in the digestive system.

Although excess weight increases the rate of type 2 diabetes, it’s worth remembering that most overweight people don’t have diabetes, and many people with type 2 are of normal weight or only moderately overweight—so again, it’s not clear-cut.

If you have a family history of type 2 diabetes, it may be difficult to figure out whether your diabetes is due to lifestyle factors or genetics. Most likely, it is due to both. But don’t lose heart! Studies show that it is possible for many people to delay or prevent type 2 by exercising and losing weight.

Identifying the genetic and environmental factors responsible for both types of diabetes has proven to be very difficult, but a lot of research continues to be done. We hope for the day when doctors can evaluate an individual’s exact genetic risk for diabetes, making it possible to avoid particular factors that would trigger the disease and help Stop Diabetes®.

For more information about the genetics of diabetes, visit our website or check out the recently published The Genetic Landscape of DiabetesThis image is associated with an external link., from the National Institutes of Health. To learn your risk for type 2 diabetes, you can take the American Diabetes Association’s Diabetes Risk Test online at http://diabetes.org/risktest.

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32 Responses to The Genetics of Diabetes

  1. Nada says:

    It is really interesting to know that genetic play a role in both type of diabetes. It used to be that T1D is inherit while T2D is due to life style. Although environmental factors trigger both, yet finding T1D’s triggers are critical. My family has a history of T2D yet my brother was the 1st to be diagnosed with T1D 14 years ago when he was 6y. Last month my youngest sister, She is 1 year younger that my brother, was diagnosed with T1D (late onset of T1D). I believe both had been introduced to the same trigger yet one was able to resist it for a while.

  2. Lois says:

    Do kids who both grandparents on mother and fathers side have more of a pre-disposition?

    • American Diabetes Association says:

      Hi Lois, this is a good question. If all four grandparents have/had diabetes, that is bound to increase a person’s diabetes risk — but it’s hard to say exactly how much. More important would be if the child’s parents didn’t have diabetes, despite the grandparents having diabetes, the child’s risk would then still be low.

      • Lisa Stevenson says:

        I am interested in knowing if there is suspicion of a cluster effect to T1D diagnoses. A few years ago I taught at a private school in the deep southeastern U.S. on our small hallway there were at least two students and three children of teachers from our hallway of six classrooms diagnosed within two years. That seems very disproportionate to the statistical odds. Even our pediatrician has said she is shocked at the increase in new cases she is seeing. Our endocrinologist has said the same. I don’t know about the other families, but we have no family history of T1D at all. Is there any research to suggest clustering due to environmental factors?

  3. Keymie Cortinas says:

    After I reading this article I was deschart two of the probability how my dauthger could got diabete type 1 . first we leave in Arizona where is almost summer in the all year , she born in there. Second she got diabete at the age of 10 she only have 1 year with diabetes. Second , She was breadfeading only in her 2 first years, Now the only reason after reading this she also was positive in walking neumonia one time in her life . I don’t know if this could have any relation butt, Walking neumonia is very common and most of the time you could have it and you don’t know it but after you got always is going to be in your blood test.

    • MLS says:

      These are possible contributing factors, not the end-all of how or why a person develops diabetes. The odds of developing type one is still about 1 in 300 to 400.

      You’re probably on to something about the Walking Pneumonia, though. Maybe it was a virus or bacteria that caused the Walking Pneumonia that was the catalyst for your daughter’s diabetes as well. I am actually very curious about narrowing down what kind of bacteria or virus could trigger the onset of type 1 and hope that more research on that comes out.

      • Lisa Stevenson says:

        My son also had a bout of walking Pneumonia, but didn’t develop T1D until several years later. I have never heard that the pneumonia will always show up in the blood. Is this true?

  4. MLS says:

    I didn’t know I could want to birth a child less than I already did, but I can say that has happened now.

    A 1 in 50 chance that my kid could develop diabetes? And I got diabetes before the age of 11? And I live in a cold environment? I knew the risks of pregnancy to my person, but that pretty much seals the deal. Not worth the risk for me or the life I’d be responsible for.

  5. Amanda says:

    My sister was diagnosed as a Type 1 diabetic at the age of 19. She was the first ever in our family and her doctors said it most likely came from a virus. She was never over weight and ate very healthy foods. After her diagnoses she became even more health conscience but the disease almost took her life. Luckily, she was gifted a kidney and pancreas transplant and is considered a “type none” diabetic. 15 years after my sisters diagnoses, my mom was diagnosed as a Type 2 diabetic. She has changed her lifestyle and is almost off all medication. We are from Florida so I doubt climate played a role in their diagnoses. Could they be linked? There are vague points in the article that suggest that but I don’t know how much I believe it. Stress is something that effects my mothers diabetes daily. The higher her stress levels seem to equate her higher blood sugar levels. But given the changes she has made to her life, she is overall healthy and happy. The biggest change she made had little to do with her exercise and eating, it was learning to manage stress.

    Clearly, I am “at risk”. Am I worried? Not really. If researchers can identify genetic and environmental triggers, that’s great…but after watching two different types of diabetics, I feel like the disease is much more complicated than that.

  6. Kathy says:

    One of my sons had undiagnosed type 1 diabetes at the age of 16. We lost him at onset, due to pnuemonia and dka. We have no known family history. I have another son who is 21. We had all the necessary bloodwork done on him two years ago (when my other son passed) and the doctor said he was fine. But should we be doing more?

    • Brianna says:

      It’s always safest to get each child tested every year or two since they are at a 50% risk of developing late onset type one

  7. ankit says:

    I m type 2 prediabetes from India. No history of parents. What is the cause of my diabetes ? I m normal weight and age 24. Taking carbophage 500 sr daily once…

  8. OKEMA PATRICO PECK says:

    I am a known person with Type 1 Diabetes.
    At-first I thought diabetes was a disease for elderly people but I was taken by astonishment on being diagonised with Diabetes when I’ve just made 17yrs old last year.
    I come to realised that formerly known “TYPE 1 DIABETES” is an Autoimmune Condition and it Mistakenly attacks the BETA CELLS in the pancreas, which produces insulin. Insulin is a hormone the body uses to convert food into energy and incase of scarsity the body system is affected accordingly.
    My great fear is that “Can we the children with Type 1 Diabetes produce and live long?????”

  9. Mary says:

    My son was diagnosed TD1 when he was 8 almost 9. He just turned 17. I recently found out that my birth mother & her family all have TD2. While I was pregnant with my daughter, I had to do the 4 hour glucose test because my blood work came back funky. The results from the 4 hour glucose test came back normal. I am curious to find out what the risk is of my daughter, she’s 3, is of her possibly developing either TD1 or TD2. My children have different fathers. Thanks!

  10. jumshaid says:

    Hello there !.
    I jumshaid I’m a 15 year old teen I have a twin sister 15 minutes older than me she had started showing symptoms of diabetes when we both were 7 years old but she got diabetes disease and now she is on insulin pen injection but after some years one day my parents told me that my sisters doctor said that I could also get diabetes too because of Harmon’s or something and my question is that CAN I GET DIABETES TOO? This thing has been disturbing me alot even tough I haven’t showed any symptoms and I get sick very rarely so please help me

    • American Diabetes Association says:

      There is a genetic basis for diabetes. Click here to learn more: http://www.diabetes.org/diabetes-basics/genetics-of-diabetes.html

    • MLS says:

      Hi, I am an identical twin, 18 minutes older, and I have diabetes while my twin does not. I have has diabetes for as long as you’ve been alive, and my sister is almost guaranteed not to develop it. That’s the thing you have to understand about type one– it’s in your genetics, you do not get diabetes like you would a cold, it is triggered.

      When I first developed diabetes, my doctor explained it a little like this: Your sister, like myself, was unlucky enough that the conditions were right for those genetics to manifest. You and my sister were lucky enough to dodge those conditions. You and my sister will always be at risk, but the longer you are exposed to the conditions that triggered the development of diabetes in us but do not in you, the less likely you are to develop it.

      You are unlikely to develop diabetes, but given you have the genetics for it, there is always the risk. Don’t let it bother you, you can’t catch it, and you can’t do anything to avoid it if you do get it. Just enjoy your life, and support your sister. Diabetes is a big disease, and the more you know about it, the better you can support your sister and the more she can rely on you to understand her situation. Don’t worry, just love.

  11. Keith Cassity says:

    Ok, so my little sister has type 1, , and im really concerned if I will get diabetes in my late teens or early twenties. Is there anyway I can prevent this, or steps that might help lower my risk.

    • American Diabetes Association says:

      Keith, at this time there is no known way to prevent or reduce your risk for type 1 diabetes.

  12. Tori Owens says:

    Hi. I’m 17 years old and my father was a Type 1 diabetic. I’m so scared ill get it and i read up on diabetes on line and try to get some info to ease my mind on it. It becomes a problem because I stress about it 24/7. He has two kids only me and my older sister witch is 30 now and she doesn’t have diabetes. She told me that his mom and a couple cousins had diabetes I think. I was diagnosed with Hypothyroidism about two months ago and I’m skinny. What is my risk of getting diabetes?? When I did my blood test for my thyroid and they checked a bunch of things like cbc test even my glucose and everything came back in range except my thyroid levels. My glucose was 81. Do you think I’ll get diabetes?

    • American Diabetes Association says:

      Hi Tori, while your father’s diabetes puts you at higher risk, there is no way to predict whether you will develop type 1 diabetes. If you want to pursue it, there are research studies that can provide autoantibody screenings. Learn more here: https://www.diabetestrialnet.org/

  13. Christian says:

    Hi, my identical twin brother was recently diagnosed with diabetes. I am so scared that I too, will be diagnosed with diabetes. At the moment, I am perfectly fine and healthy, we both are very active runners and eat very healthily. If you can spare any light on this subject I would greatly appreciate it.

  14. Robyn says:

    My Grandaughter was born with diabetes, she had a pump for a while then she has been put onto medication, we have been told that she will be able to go off this at some time. We have never heard off this before nor has a lot of doctors and no one can explaine. I hope some one knows what I’m talking about and can forward some information to us .

  15. Gaurav says:

    I am suffering from type 2 diabetes with the glucose level remains on 110-120 before meal. My wife has no diabetes and she is pregnant. What are the risk of diabetes or other complication in baby to be born? Please guide

  16. Emily says:

    My Father has type 2 diabetes and got it at the age of 45. Im a triplet and was wondering if I can have a high risk of T2D . One of my brothers has low blood sugar , while my other has a moderate one I’m also in the middle, but I’m just afraid if I can get it to. Do O have a risk of T2D if I’m a identical triplet and my fathers family history all has T2D ?

  17. Andy says:

    Hi,

    I was diagnoised T1D at the age of 11 years. My grandfather had T2D and my mother also had the diabeties but not sure which type but in the younger age at 20 years may be. I am recently married, wanted to know what are the chances of diabeties inherited to my child. Is there any chance with which i can avoid inherited to my child. Please guide me.

  18. Alicia says:

    Interesting… Just wanted to know if I was at risk. Thank!

  19. Roxy says:

    My husband’s sister developed type 1 age 7. She went on to develop coeliac, hypothyroidism and epilepsy. Sadly she recently passed away at 24 following a seizure in her sleep. My husband and I are expecting a baby and he’s worrying about the risks to our little boy. He has an aunty and uncle who are have type 2 diabetes (and both developed later in life and were overweight) and his sister had type 1 at age 7. The only history my side is my grandmother developed type 2 in her seventies. No history other than that. Could you estimate the risk to our baby? We are both well (he has asthma I have fibromyalgia) we’re both a healthy weight. Many thanks I hope you can help

  20. mos says:

    hey
    i need your help
    i will take adecicion if i marry girl or not , she has one syster with D1 when she was liten . the girl whom i will marry her has inte disesass , but his syster and his mother brother and his mother sister and one another in the children of his mother syster
    __????

  21. Jaclyn says:

    My husband is type 1 diabetic (since 17) My son is 7. I was told when pregnant my baby was at no higher risk of diabetes than anyone else but I am now feeling concerned as the affects of diabetes has had a huge impact on my husbands life and it scares me to think my boy faces the same challenges. My husband had thyroid problems as a child too causing weight gain snd bloating which I now know is linked and my son is of very solid build and becomes much sweatier than other kids from any physical activity. He was always thirsty as a child but not lathargic so the doctor seemed to think it was nothing? Any advice welcomed!!!

  22. ramesh says:

    i want to know can a man age 45 become father who has diabetes and who is living on insulindaily two times and what are complicaiton child will have please let me know

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