June 4, 2016
Genetics and Heredity
Question from Memphis, Tennessee, USA:
My wife and I are considering having our first child. We are concerned, though, because she is under the impression that the likelihood of our child having type 1 diabetes mellitus (T1DM) is very high. What she has told me is that both of her parents are carriers and both her sister and brother have T1DM. She says that T1DM goes sideways and because her siblings have it, this means that she is definitely a carrier and our child will almost certainly have T1DM. She doesn’t feel like there is a reason to go to an endocrinologist at this point because she is positive that her information is accurate. Is her understanding of this correct? If it is, what can we do, if anything, to lessen the chances of our child being born with T1DM? Her brother and sister both have such rapid onset hypoglycemia that they seize immediately. I’ve never seen anyone drop so fast.
In fact, what you describe as sideways genetic risks is not correct. The genetic risks for diseases like type 1 diabetes are only partly known and there are many other factors that interact with the genetic risks. Type 1 diabetes does not skip generations. If you knew the genetic markers for diabetes in your relatives, then you could test these same markers in yourself and your wife and know if they are present or not. This is quite expensive to do outside of research studies so is not easily done. The actual risks are about 2 to 5% for a parent who has type 1 diabetes to pass it along to their children so your wife (without diabetes) has less risk than that. That said, environmental factors also come into play. Breast feeding is protective, for instance, comes to play not because breast milk per se is protective but because it avoids cow milk exposure and perhaps some other food exposure, too. Some viruses also can be factors and perhaps some chemicals in the environment or foods we eat also may be factors. There is lots of research ongoing but no definitive answers. The single best thing to be done is exclusively breast feeding for the first 12 months of life. Not only is it better for the baby for many reasons, but also decreases the risk of developing type 1 diabetes. Also, some research suggests avoiding all gluten-containing foods also may decrease risks of type 1 diabetes. If you still have some questions, it is best to get a consultation either with a well respective diabetologist or with a genetics specialist for more individualized counseling.
[Editor’s comment: You may wish to contact TrialNet to determine if your wife is eligible to participate in their studies.