October 26, 2006
A1c (Glycohemoglobin, HgbA1c), Genetics and Heredity
Question from Pittsburgh, Pennsylvania, USA:
Can you tell me if having type 1 diabetes will predispose a person to having any of the “antibodies” or “genetic markers” that are found in a person with confirmed celiac disease? I realize the autoimmune aspect of diabetes will increase the risk of celiac disease and other autoimmune disorders, but I am specifically concerned about celiac and diabetes and there being some sort of “crossover” of the serologic markers, either the specific genes or a certain antibody that will be present in both the diabetic patient and the celiac patient due to the autoimmune nature of both diseases.
Also, as a long-time diabetes patient, my son has had A1cs done at least three times a year for 15 years; I have most of these records and the test results range from low 6s to a high-end test of 7.6. His current endocrinologist has classified his care as “overall inadequate control” over his lifetime with diabetes. I thought we were doing a good job; he has no side effects, perfect retinas and has always tested in range for kidney and thyroid function. In your opinion, is this A1c history “inadequate”?
Our understanding about the autoimmune nature of type 1 diabetes and celiac disease suggests that there is an inherited genetic risk associated with the HLA region of our chromosomes. Then, something else, not exactly well defined, must happen to “trigger” this risk and produce damage to the beta cells, the gut lining, the thyroid gland, the adrenal gland, etc. For celiac, we know that this is exposure to wheat/gluten. But, one disease does not cause the others and there is no known overlap with these antibodies except that in a type 1 diabetes population, about 20 to 40% will also have positive thyroid antibodies, about 10 to 20% will have hypothyroidism, about 1 to 2% hyperthyroidism, less than 1% will have adrenal antibodies and Addison’s and about 6 to 10% will have celiac antibodies. The overlap is in the genetic susceptibility genes, according to our current understanding. There is some theoretical research that suggests that avoiding cows’ milk protein and avoiding wheat/gluten (especially the first 12 months of life) would also decrease (maybe prevent or only postpone) type 1 diabetes, but this is not confirmed research.
I think that you are doing better than average if the A1c values range in the 6 to 7.6 range throughout his diabetes lifetime. However, normal values are 4 to 6% so, perhaps, the comment reflects that fact of our inability to have normal blood glucose values all the time. If you can get to the below 7% range, this will reduce long-term risks further, but this is a difficult task, of course.