My mom has diabetes

Genetics of Diabetes

Learn the Genetics of Diabetes

You’ve probably wondered how you developed diabetes. You may worry that your children will develop it too.

Unlike some traits, diabetes does not seem to be inherited in a simple pattern. Yet clearly, some people are born more likely to develop diabetes than others.

What leads to diabetes?

Type 1 and type 2 diabetes have different causes. Yet two factors are important in both. You inherit a predisposition to the disease, then something in your environment triggers it.

Genes alone are not enough. One proof of this is identical twins. Identical twins have identical genes. Yet when one twin has type 1 diabetes, the other gets the disease at most only half the time. When one twin has type 2 diabetes, the other’s risk is at most 3 in 4.

Type 1 diabetes

In most cases of type 1 diabetes, people need to inherit risk factors from both parents. We think these factors must be more common in whites because whites have the highest rate of type 1 diabetes.

Because most people who are at risk do not get diabetes, researchers want to find out what the environmental triggers are. One trigger might be related to cold weather. Type 1 diabetes develops more often in winter than summer and is more common in places with cold climates. Another trigger might be viruses. Perhaps a virus that has only mild effects on most people triggers type 1 diabetes in others.

Early diet may also play a role. Type 1 diabetes is less common in people who were breastfed and in those who first ate solid foods at later ages.

In many people, the development of type 1 diabetes seems to take many years. In experiments that followed relatives of people with type 1 diabetes, researchers found that most of those who later got diabetes had certain autoantibodies in their blood for years before. (Antibodies are proteins that destroy bacteria or viruses. Autoantibodies are antibodies ‘gone bad’ that attack the body’s own tissues.)

Type 1: Your child’s risk

If you are a man with type 1 diabetes, the odds of your child developing diabetes are 1 in 17. If you are a woman with type 1 diabetes and your child was born before you were 25, your child’s risk is 1 in 25; if your child was born after you turned 25, your child’s risk is 1 in 100.

Your child’s risk is doubled if you developed diabetes before age 11. If both you and your partner have type 1 diabetes, the risk is between 1 in 10 and 1 in 4.

There is an exception to these numbers. About 1 in every 7 people with type 1 diabetes has a condition called type 2 polyglandular autoimmune syndrome. In addition to having diabetes, these people also have thyroid disease and a poorly working adrenal gland. Some also have other immune system disorders. If you have this syndrome, your child’s risk of getting the syndrome—including type 1 diabetes—is 1 in 2.

Researchers are learning how to predict a person’s odds of getting diabetes. For example, most whites with type 1 diabetes have genes called HLA-DR3 or HLA-DR4. If you and your child are white and share these genes, your child’s risk is higher. (Suspect genes in other ethnic groups are less well studied. The HLA-DR7 gene may put African Americans at risk, and the HLA-DR9 gene may put Japanese at risk.)

Other tests can also make your child’s risk clearer. A special test that tells how the body responds to glucose can tell which school-aged children are most at risk.

Another more expensive test can be done for children who have siblings with type 1 diabetes. This test measures antibodies to insulin, to islet cells in the pancreas, or to an enzyme called glutamic acid decarboxylase. High levels can indicate that a child has a higher risk of developing type 1 diabetes.

Type 2 diabetes

Type 2 diabetes has a stronger link to family history and lineage than type 1, and studies of twins have shown that genetics play a very strong role in the development of type 2 diabetes.

Yet it also depends on environmental factors. Lifestyle also influences the development of type 2 diabetes. Obesity tends to run in families, and families tend to have similar eating and exercise habits.

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 genetic susceptibility. Most likely it is due to both. However, don’t lose heart. Studies show that it is possible to delay or prevent type 2 diabetes by exercising and losing weight.

Have you recently been diagnosed with type 2 diabetes? Join our free Living With Type 2 Diabetes program and get the information and support you need to live well with diabetes.

Type 2: Your child’s risk

Type 2 diabetes runs in families. In part, this tendency is due to children learning bad habits—eating a poor diet, not exercising—from their parents. But there is also a genetic basis.

More information on genetics

If you would like to learn more about the genetics of all forms of diabetes, the National Institutes of Health has published The Genetic Landscape of Diabetes. This free online book provides an overview of the current knowledge about the genetics of type 1 and type 2 diabetes, as well other less common forms of diabetes. The book is written for healthcare professionals and for people with diabetes interested in learning more about the disease.

To Breed or Not to Breed: the Genetic Risks of Diabetes

By David Greene, PhD on February 14, 2019 / Genetic Risks of Diabetes

My grandmother was diagnosed with type 1 diabetes as an adult, a highly unusual occurrence back in the late 1940’s. As a child, I didn’t even know she had diabetes. I did know she always carried a Chunky in her purse. You remember those wonderful hunks of milk chocolate deliciousness. She used them to treat low blood sugar, although I always thought they were for me. Along with the occasional Chunky, she also passed along diabetes. I was diagnosed with type 1 when I was ten years old.

My grandmother developed diabetes after she was done having children. In contrast, I had ample time to think about my decision. Having a child is an irreversible, life-altering decision. Philosopher Christine Overall believes that deciding to have a child is the biggest ethical decision we will ever make. Indeed.

What Are the Odds?

The genetic risk of having a child with type 1 diabetes is not entirely understood and fluctuates greatly. If the father has type 1, the child has between a 6% and 8% chance of developing diabetes. If the mother has type 1, the risk can range from 2% to 3%. If both parents have type 1 diabetes, the risk increases to 25%. There are a number of contributing factors to explain the differences. The younger the parent was when diagnosed, being Caucasian, and the child having an early history of certain childhood traumas and infections increases the odds. The older the parent was when the child was born and the longer the mother breast fed decreases the odds. There are also environmental factors to consider such as living in a cold climate and early dietary variables that can impact risk.

The genetic risk associated with type 2 diabetes is also complex. If the father has type 2, the risk factor is about 30%, slightly higher if it is the mother. If both parents have diabetes, the risk factor jumps to about 70%. There are a number of factors that impact the risk, such as obesity, sedentary lifestyles, poor dietary practices, smoking, elevated blood pressure, and a history of gestational diabetes. All increase the risk.

The Times, They Are a Changing (with thanks to Bob Dylan)

My decision to have a child was not all about odds and statistics. I also addressed the issue of my child’s quality of life living with diabetes. I was discharged from the hospital on my eleventh birthday, 1966. My physician assured me there would be a cure within five years. He missed, several times over. My, oh my, did he miss. Just the same, I’ve seen some pretty impressive advances. I have experienced glass and disposable syringes, animal and analog insulin, urine and blood testing, continuous glucose monitors, and insulin pumps. The quality of my life has improved dramatically, and I believe I am handing off a future with great possibilities. I have to believe a cure is much closer than it was in 1966, when it was a mere five years away.

I’m Only Human

I’m also aware of some psychological influences on my decision making. Like most people, mine is curiously flawed. When dealing with personal issues, I can be unrealistically optimistic. Unrealistic optimism allows us to perceive ourselves and our situations favorably. This is not all bad as it helps us to feel better about ourselves, fend off depression, and deal with all those pesky life annoyances. It can also lead us to believe we can beat the odds, particularly when the odds are not overwhelming. If I am willing to believe that I can beat the odds of maintaining a successful marriage, I can certainly beat the odds that my child might develop diabetes.

Strange Bedfellows

I tend to be a bit academic. I like research, statistics, and psychology. But I found that none of this resulted in a formula to make this decision. My wife and I decided to have a child. It was a deeply personal, intuitive, and optimistic decision. He is now 27 years old and diabetes free. But I still worry. From the very beginning I was warned by his pediatrician not to overdo it testing his blood sugar every time he peed “too often”. With each passing year I have been thankful he hasn’t had to deal with diabetes. Not that he couldn’t, just that he didn’t need to. Ultimately, our decision to have a child was not academic. There were no guarantees, one way or the other. We just had to decide what was right for us.

Are You At Risk for Gestational Diabetes?

Gestational diabetes, also known as diabetes mellitus, is a condition in which too much sugar stays in the blood rather than being used for energy. Some women are at risk via their current medical status and/or lifestyle choices. Other times, it is diagnosed in women who have never struggled with blood sugar issues in their life. In either scenario, gestational diabetes poses a health risk to both mother and baby, which is why healthcare providers work so carefully to avoid it, and treat it immediately once it is diagnosed.

What is Gestational Diabetes?

Gestational diabetes is typically diagnosed around the 24th week of pregnancy, via a glucose screening test, when a mother’s blood sugar levels are consistently higher than they should be. In most cases, women diagnosed with gestational diabetes have never had diabetes before and will not have it again. While its causes are not completely understood, it is thought the hormones produced in the placenta block the mother’s natural insulin processes, causing insulin resistance, which makes it harder for her body to regular blood sugar levels.

Once your body is no longer able to make and use the correct amount of insulin to convert glucose (sugar) into energy, glucose levels begin to rise. This condition is called hyperglycemia. All that extra glucose passes through the blood stream, into the placenta, through the umbilical cord and directly into your baby. This is where things can become unhealthy for both you and baby.

Now, your baby’s body is working overtime, trying to produce enough insulin via his or her own pancreas to handle all that extra sugar. In the meantime, all that extra sugar (energy) isn’t being used so it starts packing on as extra fat pounds. This leads to a condition called macrosomia, or a “fat” baby.

Risks for developing GD include:

  • Being 25 years or older when you get pregnant. Gestational diabetes risk increases after age 25 and with each passing year.
  • Family medical history. If your mother, grandmothers and/or sisters had gestational diabetes, you’re more likely to have it as well.
  • Personal medical history. If you are pre-diabetic or have higher-than-normal blood sugar levels before pregnancy, you’re more likely to develop gestational diabetes.
  • Excess weight. Try to keep your body mass index (BMI) below 30 to minimize risk.
  • Non-white ethnicity. Women who are of Latin, Asian and African decent are at higher risk for gestational diabetes.

Gestational Diabetes Leads to Several Health Risks for Mother & Baby

Fat babies are cute, but babies with macrosomia are heavier than nature intended. Plus, as you can imagine, all that extra weight is bad for mama and baby when it comes time for labor and delivery. Some of the health risks caused by gestational diabetes include:

Extra-large babies. Now, the reality is that your body was designed to birth a baby naturally – and healthy babies can range from six to ten pounds on average. However, “naturally” is the key word. Gestational diabetes leads to UN-natural weight gain, and this can cause baby to struggle when it’s time to get through the birth canal, putting you at risk for a C-Section.

Pre-term birth leading to respiratory distress. If you have gestational diabetes, your doctor may decide your baby needs to be born earlier, rather than full-term, because he’s getting too big. Babies born pre-term can lack fully developed lungs, which can lead to respiratory distress syndrome and a risk of further complications.

Low blood sugar after birth. For every action, there is an equal and opposite re-action, right? Thus, many babies who have all that extra glucose in their system (via the mother) have increased insulin production. Once out of the womb, this can cause severely low blood sugar levels (called hypoglycemia). In infants, severe hypoglycemia can cause seizures.

Higher risk of Type 2 diabetes. Babies born of mothers with GD have a higher risk of developing type 2 diabetes later in life. If you have gestational diabetes, you are also more likely to develop type 2 diabetes when you get older.

Infant mortality. In cases where gestational diabetes goes untreated, it can lead to infant death.

Risk of high blood pressure and pre-eclampsia. Women with gestational diabetes have higher rates of high blood pressure and are at higher risk for developing a very dangerous condition called pre-eclampsia.

All of the above are examples of why prenatal care is so important. Catching gestational diabetes before it becomes a problem is integral to the health of you and your baby. Once diagnosed, your doctor will work closely with you on diet and lifestyle changes that can naturally reduce blood sugar levels. She will continue to monitor you and your baby carefully, ensuring you are both as healthy as possible. If necessary, medications may be prescribed to further keep blood sugar levels in check.

Having a Parent With Type 2 Diabetes: What to Know About Your Risk

Every year, Allison Jones, age 34, of Champaign, Illinois, gets her blood sugar checked. So far, she has breathed a sigh of relief when her numbers have come back normal each time. Still, she knows that type 2 diabetes is in her blood, or more precisely, her genes. She’s watched her father, diagnosed in his 40s, struggle with the disease, and three of her father’s four siblings also have it. “It’s definitely a worry in my mind,” Jones says.

Genetics and Lifestyle Play a Role

Jones’s concern is well founded. Research suggests that having a parent with type 2 diabetes increases your risk of developing the disease by as much as fourfold, and even more if both parents are affected. “We know that if both parents have type 2 diabetes, there’s about a 50 percent risk that you and your siblings could have the genes passed on,” says Edward Hess, MD, an endocrinologist who leads the diabetes program at Kaiser Permanente in Fontana, California.

It’s clear that there’s a strong genetic component to type 2 diabetes, and that’s why we see greater prevalence in some ethnic groups, like Native Americans and African Americans. But it’s an incredibly complex disease. “There are literally dozens of genes and sites on the DNA that are associated with type 2 diabetes,” Dr. Hess says.

It’s hard to tease out how much of our risk comes from genetics and how much comes from lifestyle factors, like eating and exercise patterns. “It’s a combination of inheriting that really strong type of diabetes from your parents,” says Hess, “and you can inherit bad habits from your parents, too.”

Understand Your Individual Risk

Family history is just one of many risk factors for type 2 diabetes, so it’s worth talking with your doctor about your overall risk. If you have a parent or sibling affected and you’re overweight or obese, the American Diabetes Association recommends getting tested for diabetes. If you have a normal BMI, they recommend routine testing starting at age 45. This is done with a blood test for blood sugar, or A1C, a measure of your average blood sugar over the last two to three months. If you have more risk factors or your test results indicate that you have prediabetes, your doctor will probably want to keep tabs on you with an annual test.

With your family history, you and your doctor should also keep an eye out for signs of diabetes complications, like vision problems or nerve damage, Hess says.

Avoid Hereditary Diabetes

While you can’t change your family tree, there is a lot you can do to cut your chances of developing diabetes. A study published in August 2017 in Primary Care Diabetes found that diet and exercise can help lead to lasting health benefits in relatives of people with type 2 diabetes. More generally, a study published in November 2009 in The Lancet showed that the Diabetes Prevention Program, which helped high-risk adults lose 7 percent of body weight and start doing about 30 minutes of moderate-intensity physical activity — like brisk walking — each day, decreased participants’ risk of diabetes even 10 years later.

Having regular, balanced meals can help even out your blood sugar so your body doesn’t have to work so hard to keep it in check, says Sandra Arevalo, RDN, CDE, the director of nutrition services and outreach programs at Montefiore Health System’s Community Programs in the Bronx, New York. She recommends three meals per day using the MyPlate eating pattern, with fruits and vegetables making up about half of each meal and a modest serving of carbohydrates, preferably whole grains.

Regular exercise is just as important. “When you are exercising, it’s like the cells open the doors to receive all the sugars in the blood, so it’s like a natural medicine for diabetes and prediabetes,” says Arevalo. She says that a registered dietitian or diabetes educator can help people make a diabetes prevention plan that will work for them.

It’s best if diabetes prevention becomes a family affair, says Hess. “Go to your brothers and sisters and say, ‘Hey, you’d better get involved in this, too, because if I’ve got this risk of diabetes, you do too.’”

Your Genes

There’s no diabetes gene that gets turned on or off to give you type 1. Instead, a bunch of them play a role, including a dozen or so that have the biggest say: the HLA genes. They make proteins your immune system uses to keep you healthy. Since type 1 diabetes is an autoimmune disease — your body destroys the cells that make insulin — it makes sense that HLA genes are front and center.

There are thousands of versions of them in the human gene pool. Which ones you get from your parents affect your chances of diabetes in a big way. Some make you more likely to get it, while others can help protect you from it. You have type 1 if your body makes little or no insulin, a hormone that helps your body turn sugar into energy.

Certain genes are more common in one group of people than in another. That’s why race and ethnicity affect things, too. For example, white people are more likely to have type 1 diabetes than others.

But even if you have genes that make you more likely to get type 1, that doesn’t mean you definitely will. Even with identical twins — who have the same exact genes — sometimes one gets it and the other doesn’t. That’s where the environment comes into play.

Family Health History and Diabetes

If you have a mother, father, sister, or brother with diabetes, you are more likely to get diabetes yourself. You are also more likely to have prediabetes. Talk to your doctor about your family health history of diabetes. Your doctor can help you take steps to prevent or delay diabetes, and reverse prediabetes if you have it.

Over 30 million people have diabetes. People with diabetes have levels of blood sugar that are too high. The different types of diabetes include type 1 diabetes, type 2 diabetes, and gestational diabetes. Diabetes can cause serious health problems, including heart disease, kidney problems, stroke, blindness, and the need for lower leg amputations.

People with prediabetes have levels of blood sugar that are higher than normal, but not high enough for them to be diagnosed with diabetes. People with prediabetes are more likely to get type 2 diabetes. About 84 million people in the United States have prediabetes, but most of them don’t know they have it. If you have prediabetes, you can take steps to reverse it and prevent or delay diabetes—but not if you don’t know that you have it. Could you have prediabetes? Take this testexternal icon to find out.

If you have a family health history of diabetes, you are more likely to have prediabetes and develop diabetes. You are also more likely to get type 2 diabetes if you have had gestational diabetes, are overweight or obese, or are African American, American Indian, Asian American, Pacific Islander, or Hispanic. Learning about your family health history of diabetes is an important step in finding out if you have prediabetes and knowing if you are more likely to get diabetes. You can use the Surgeon General’s family health history tool, My Family Health Portraitexternal icon, to collect your family health history of diabetes and find out your risk of getting diabetes. Be sure to let your doctor know about your family health history of diabetes, especially if you have a mother, father, sister, or brother with diabetes. Your doctor might recommend that you have screening for diabetes earlier.

Even if you have a family health history of diabetes, you can prevent or delay type 2 diabetes by eating healthier, being physically active, and maintaining or reaching a healthy weight. This is especially important if you have prediabetes, and taking these steps can reverse prediabetes.

Does your mom, dad, sister, or brother have type 2 diabetes?

If so, you could have prediabetes and are more likely to get type 2 diabetes yourself. But there are important steps you can take to prevent type 2 diabetes and reverse prediabetes if you have it.

  • Take this testexternal icon to find out if you could have prediabetes.
  • Ask your doctor whether you need earlier screening for diabetes.
  • Learn more about how to prevent type 2 diabetes:
    • National Diabetes Prevention Program: Find out more about the lifestyle change program and how to find a program near you.
    • National Diabetes Education Program: Find tip sheets and tools on preventing type 2 diabetes.
    • Reverse Prediabetesexternal icon: Find out more about joining a diabetes prevention program and learn lifestyle tips for managing your weight, exercising, eating healthy, and quitting smoking to help reverse prediabetes and prevent type 2 diabetes.
    • Take the Family Health History Quizexternal icon to learn more about family health history and diabetes, and learn how to prevent type 2 diabetesexternal icon.

More Information

  • Diabetes
  • National Diabetes Prevention Program
  • National Diabetes Education Program
  • Prevent Diabetes STATexternal icon
  • Do I Have Prediabetes?external icon
  • Risk Factors for Type 2 Diabetesexternal icon
  • Preventing Type 2 Diabetesexternal icon
  • Native Diabetes Wellness Program

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