My five-year-old daughter who has type 1 was recently diagnosed with hypothyroidism. How will Synthroid affect her NovoLog and Lantus/blood sugars?

Your doctors probably told you that thyroid disease (usually an underactive thyroid, called hypothyroidism) occurs very commonly with type 1 diabetes. Some estimates go as high as 20%. Both are associated with the immune system creating “antibodies that attack” the normal glandular tissue.

There are many brands of thyroid hormone replacement. The brand Synthroid perhaps is the most well known. People do tend to call most any form of thyroid replacement as “Synthroid” in the same way that many people refer to all facial tissue as “Kleenex.” So, don’t be surprised if you get a different, and even less expensive, brand.

For almost all intents and purposes, the replacement of thyroid hormone will have little effect on blood glucose regulation for the patient with diabetes. If the patient has been fairly significantly hypothyroid, then with the improvement of the metabolic rate with the addition of the thyroid hormone, the doses of insulin may be metabolized slightly faster and not last as long. This could possibly lead to less effect of the insulin and the insulin doses then would require some minor adjustments. Certainly, as in any situation when you recognize that blood glucose patterns are changing, you would want to talk to your own diabetes team.

DS