September 29, 2003
Diagnosis and Symptoms
Question from Atlanta, Georgia, USA:
Two years ago, my 17 year old son was diagnosed with type 1 diabetes. He had minimal symptoms (no excessive thirst, weight loss, etc.) but had not been feeling well for a number of months. They found sugar in his urine (but no ketones) during a routine physical, his fasting blood sugar was high, his two-hour post-meal blood sugar was 248 mg/dl [13.8 mmol/L], and his five-hour post-meal blood sugar was 144 mg/dl [8 mmol/L]. His A1c was 6.7%. At the time, he was 5 feet 8 inches tall, weighed 150 pounds, and the pediatric endocrinologist ruled out type 2 diabetes. Two years later, he is still on the same low dose of insulin (10 units of NPH with 3 units of Regular in the morning, 6 units of NPH with 3 units of Regular before dinner. His glucose levels are very steady, 80-120 mg/dl [4.4-6.7 mmol/L], averaging around 110 mg/dl [6.6 mmol/L]. We assumed this was an extended honeymoon period, but we recently switched doctors for insurance reasons, and the adult endocrinologist did some new tests. The C-peptide was positive and the GAD antibody was negative. He says this means that my son has type 2 diabetes. I am wondering about this since my son was never obese, although he was pretty sedentary.
It has been recognised for some years that it may be difficult at the onset to distinguish some cases of type 1A (autoimmune) diabetes from all the other types of diabetes that have their onset in childhood. A two year honeymoon period is rare, but not unheard of. However, it was entirely appropriate to get the C-peptide and anti-GAD antibody levels.
I think though that you need to ask the endocrinologist what he means by a ‘positive’ C-peptide test because some C-peptide can persist in type 1A diabetes for two years, but an actual level that was normal or a little high would suggest type 2. Likewise, the negative anti-GAD test is a strong point against type 1 but not quite conclusive without a negative ICA 512 and an anti-insulin test as well. There are some other less common possibilities like type 1B diabetes, but what is much more important than a specific diagnosis is to keep blood sugar levels as near to normal as possible and by the simplest means.