January 3, 2001
Diagnosis and Symptoms
Question from Alameda, California, USA:
I was diagnosed with diabetes nearly four years ago, at age 33. The classic symptoms developed over a period of about two weeks. At the time, I was very overweight (over 200 pounds), but not remarkably sedentary. My doctors assumed that I had type 2, put me on medication, and told me to lose weight. They did not do a C-peptide test. I started dieting and exercising obsessively and lost about 80 pounds over the next nine months. The weight seemed almost to melt off, which was very different from my previous experiences with dieting. However, I couldn’t get my blood sugar in control. Various oral medications would appear to work for a few weeks, and then my blood sugar would rise again. Finally, my doctor put me on insulin, and my blood sugar plummeted from above 300 to 80 mg/dl [16.7 to 4.4 mmol/L] overnight. It turned out that, far from being insulin resistance, I am very insulin sensitive. My endocrinologist concluded that I was a type 1 after all. I asked to have a C-peptide test done, but she refused. (I think she believed that if I found out that I was producing any insulin at all, I’d want to stop the insulin shots — which just showed how badly she understood me!) I recently moved and started going to a new endocrinologist. He ordered a C-peptide test, which came out 0.2 (fasting). My understanding is that this means that I’m still producing a tiny bit of insulin, but such a small amount that I fit the diagnostic criteria for type 1. I’m now using an insulin pump and doing well. I’ve also managed to keep off most of the weight I lost during those terrifying nine months.
So, here are my questions:
Is it possible for a type 1 to go for nine months without taking insulin, and without showing any sign of DKA?
I have heard that when adults develop type 1, the beta cells die off more slowly than they do with children. Is it possible that this happened to me?
When an individual is taking insulin, does this affect the accuracy of the C-peptide test?
Can I expect my pancreas to produce less and less insulin over time?
Answer:
Unfortunately, your experience is similar to other patients with type 1 diabetes. It is true that when individuals present with type 1 diabetes later in life (over age 30) there is a tendency for the type 1A (autoimmune) to be destroyed over a more protracted course. Therefore, instead of presenting with DKA [diabetic ketoacidosis], these patients present with hyperglycemia refractory to oral agents. They have enough residual insulin secretion left to avoid DKA, but cannot maintain normal glucose levels.
We have referred to this presentation as Late-onset Autoimmune Diabetes of Adulthood. It is associated with positive antibodies specific to beta cells, such as GAD. It is not the case that if you are insulin it will make the measurement of type 1A (autoimmune) levels less accurate. However, if your glucose levels are in the near-normal range, there is not a stimulus to produce high C-peptide levels. That is why this can be performed as part of a dynamic test utilizing a test meal or taken during the post-meal state when blood sugars usually rise. As far as whether C-peptide levels will continue to fall, this is the usual pattern for type 1A diabetes. However, as seen with a traditional honeymoon period, the better you control your diabetes, the slower the decline in insulin secretion.
Good luck. It sounds like you are working hard and learning a lot about diabetes.
JTL
