Question from Chicago, Illinois, USA:

My daughter was diagnosed with type 1 diabetes over three years ago and has been using a insulin pump for the last year. However, high A1cs, weight gain, irregular periods and some acne suggested to her doctor that she also had PCOS and associated insulin resistance. Because she is now almost 18, my daughter recently began seeing an adult endocrinologist who prescribed Glucophage during first visit. We asked if this meant that she had type 2 diabetes, and the endocrinologist gave us the following response:

[The pediatric endocrinologist] did not send me any of the laboratory forms, so I cannot tell all of the labs she may have done. Typically, pediatric endocrinologists check the insulin autoantibodies (IAA) and the islet cell antibodies (ICA) at diagnosis. The GAD antibodies are used more often for type 1 diabetes suspected in adult patients. I didn’t see any ICA results, but she certainly had a positive IAA result documented on the flow sheet, so her type 1 diabetes is confirmed.

There is no question that individuals with PCOS are prone to developing type 2 diabetes mellitus. However, a number of individuals with type 1 diabetes would have developed type 2 diabetes later in life if their pancreas had not already been destroyed by the immune malresponse.

Essentially, it appears to me that the new endocrinologist is saying that my daughter has both type 1 and type 2 diabetes, the latter the probable consequence of PCOS and insulin resistance. My daughter’s main concern (remember, she is a teenager) is her weight and the Glucophage insert warns that using Glucophage with insulin may cause weight gain, although the typical result of using Glucophage is weight loss.

Can you comment on using Glucophage in type 1 diabetes generally? What is the possibility of my daughter having both type 1 and type 2 diabetes? Can she expect further weight gain as a result of taking Glucophage in addition to insulin therapy?