April 3, 2003
Diagnosis and Symptoms
Question from Burlington, North Carolina, USA:
A few weeks ago, I posed a question about having a dramatic drop in insulin needs since pregnancy. I had the C-peptide done for two hours after a meal and then fasting. The two hour test results was 1.8, the fasting was 1.0, and my doctor said they were off by only a few points from normal. How can I have these C-peptide levels if I am supposed to have type 1 diabetes? Is it possible that pancreas tumors can make even a type 1 produce insulin? What types of tests can be done to check for a pancreas tumor?
I would suggest that interpretation of the C-peptide levels can be perceived in a different way. First, all C-peptide measurements need to be interpreted in light of the simultaneous blood glucose level. If the glucose is low in a normal person, the C-peptide level would probably be low too. Second, the two-hour C-peptide is not high. If the glucose was also high, this would represent an inappropriately low level of C-peptide for a high blood glucose.
The most significant reason for your decrease in insulin requirements after pregnancy is the loss of a growth hormone-like hormone that is made by the placenta. This hormone antagonizes insulin’s effects. When the placenta is delivered the hormone levels go down. This allows for more insulin sensitivity and decreased insulin requirements.