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January 17, 2011

Diagnosis and Symptoms, Genetics and Heredity

Question from Albany, New York, USA:

I love learning and endocrinology (yeah, I'm a dork) and have so many questions I could ask, but I'll keep it to two: I've been hearing more about adults being diagnosed with type 1. Is there the same genetic/familial predisposition, albeit small, for family members of those diagnosed as adults compared to those diagnosed as children? My father is a type 1 diabetic diagnosed in his 30s (a few years before I was born). Out of curiosity, my family and I have occasionally checked my blood sugar and, while I am confident I am not a diabetic, we have noticed something. If it's checked fasting, it's often elevated (110 to 140s mg/dl [6.1 to 8.2 mmol/L]) but during the daytime, it's usually completely normal (50s to 90s mg/dl [2.8 to 5.5 mol/L]) with occasional higher numbers (150 to 190s mg/dl [8.3 to 11.0 mmol/L]). Why is it really only high in the morning? Is this a normal part of daily fluctuations or should I bring this up at my next physical? Should I be concerned about anything in the future?


The genetics of type 1 diabetes appear to be similar for those who develop type 1 diabetes later on as those who develop diabetes as young people. Why there is a slow onset of type 1 diabetes, as if the immune destruction is slower and more prolonged, is not known. Clearly, these patients have a different genetic inheritance pattern from those with type 2 diabetes. The patients with type 1 diabetes have a risk of approximately 10% if one of their parents had type 1 diabetes. It is a bit higher if the father has type 1 diabetes than if the mother has type 1 diabetes. Patients with late-onset type 1 diabetes have positive antibody markers, such as anti-GAD antibody, similar to younger patients. What controls the pace of the onset of beta cell destruction is not known.

A normal fasting glucose is considered to be less than 100 mg/dl [5.6 mmol/L. Two values > 126mg/dl [7.0 mmol/L] is considered diabetes. The problem with relying on fingerstick blood sugars is that this instrument lacks the precision to make an accurate diagnosis. They are okay for the management of diabetes, but not diagnosis. I would recommend you discuss this with your physician at your next visit. It is not that it is an emergency, but the numbers need to be put in the correct light. I would let your physician know sooner, rather than later, if you have symptoms, such as unexplained weight loss, frequent urination, persistent thirst, or blurring of vision.