From Philadelphia, Pennsylvania, USA:
My 10 year old daughter had an A1c of 11.9% when she was diagnosed with type 1 diabetes four months ago, and now it is 5.8%, but her numbers aren't really great. I also asked to have her thyroid tested, and her T4 [a thyroid test] was normal, but her TSH was 7.81 (a little high). She has also been maturing for about a year now. Her doctor is happy with her A1c and wants to wait three months to recheck her TSH, but my gut tells me something is off.
How can she have that A1c without having great readings? Is it possible that something else is going on? Should I be concerned?
Firstly, it may help to review what the hemoglobin A1c is measuring -- the percentage of glucose "stuck" to hemoglobin in red blood cells. The average recycling time for a red blood cell (and essentially hemoglobin) is about 120 days, but at any moment in time, you are destroying old hemoglobin (so no glucose attached to it any longer) and making brand new hemoglobin (with no glucose yet attached). So the A1c is giving you an average glucose-hemoglobin complex over the past 8-10 weeks or so.
After four months of diabetes, I expect an improvement in the A1c. You state that the glucose levels have not great, but I don't think I really know what that means. Between 80-180 mg/dl [4.4-10 mmol/L] about 75% of the time? I'd say that's good! However, remember that when you check the glucose reading before meals and at bedtime, and perhaps a couple of other checks, you are checking at that minute but there are 1440 minutes during the day. So the HbA1c gives insight as to the glucose levels "all the other times." Can you have a "falsely low" HbA1c value (i.e.,a value that measures low for some reason other than good glucose control)? Yes, but not commonly. It usually occurs in folks who have some types of anemia and therefore irregularities of the hemoglobin portion of the glucose-hemoglobin complex.
So, I'd have you go back to basics: make sure that your daughter's meter is calibrated, use the control solution. If she has a meter that uses a chip that must change with each bottle of test strips, be sure that the meter code and the chip are the same. Be certain that you and your daughter's diabetes team have concrete goals as to her target glucose ranges. If all looks good, then I'd put the emphasis on the HbA1c value but watch meal planning carefully to avoid high post-meal readings. (I am presuming that you check before meals and at bedtime.)
The TSH value of 7.8 is high, and I agree in rechecking it in two to three months. If your daughter also has thyroid antibodies, I would view the TSH to be reflective of a true underactive thyroid gland and would agree with starting thyroid replacement therapy.
Original posting 14 Apr 2002
Posted to Thyroid
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