Abstract
A 56-year-old female was diagnosed with type 2 diabetes mellitus 15 years ago and had been treated with several oral hypoglycemic agents, but her glycemic control was poor. She was admitted to our hospital yearly and always showed negative results for anti-GAD antibodies (GADAb). At her last admission, she had a low titer of GADAb (4.6 U/ml), and insulin therapy was started. At that point, her urinary C-peptide level was 77 μg/day. Ten months later, she was admitted to our hospital again, and her laboratory data showed the following: HbA1c level, 9.7 %; serum C-peptide levels after fasting and 2 h after breakfast, 0.7 ng/ml and 2.1 ng/ml, respectively; mean urinary C-peptide level, 18.5 (22.1/14.8) μg/day; increase in the serum C-peptide level six minutes after the intravenous loading of glucagon (1 mg), 1 ng/ml; and the titer of GADAb, 1.2 U/ml. In the current case, the titer of GADAb was initially low, and its positive period was short, last only 10 months. During this period, the endogenous insulin secretion decreased remarkably. Based on these findings, it was thought that the decrease of insulin secretion in this case was associated with an autoimmune mechanism.
