Type 1 diabetes manifested solely by 2-h oral glucose tolerance test criteria

The clinical presentation of type 1 diabetes usually involves symptoms such as polyuria and polydipsia. However, investigators in the Diabetes Prevent ion Trial of Type 1 Diabetes (DPT-1) have detected a group of subjects with type 1 diabetes who have a different phenotype. These subjects are asympto matic, have normal (<6.1 mmol/l) (group A) or impaired (6.1- <7.0 mmol/l) ( group B) fasting glucose, but have 2-h glucose values >11.1 mmol/l on their oral glucose tolerance tests (OGTT). of the 585 OGTTs performed on islet c ell antibody (ICA)-positive relatives with insulin autoantibodies (IAA) or low first-phase insulin response (FPIR), normal glucose tolerance (NGT) was found in 427 subjects; impaired glucose tolerance (IGT) was found in 87 su bjects, and diabetes was found by 2-h OGTT criteria alone in 61 subjects. D espite marked differences in 2-h glucose values (NGT 5.8 +/- 1.1 mmol/l, IG T 8.9 +/- 0.9 mmol/l, and group A 13.5 +/- 2.5 mmol/l), there were no signi ficant differences in fasting glucose values among NGT (4.8 +/- 0.5 mmol/l) , IGT (5.03 +/- 0.5 mmol/l), and gronp A (4.99 +/- 0.7 mmol/l) categories. Mean FPIR was higher in subjects with NGT compared with subjects with IGT a nd subjects diagnosed by 2-h OGTT criteria alone. However, the correlation between FPIR and 2-h glucose value was low (r(2) = 0.14). Multivariate anal ysis demonstrated that additional independent variables provide smaller con tributions to the 2-h glucose value. In conclusion, there are asymptomatic type 1 diabetic subjects whose diabetes was diagnosed by the 2-h criteria o n OGTT alone. Despite the importance of beta -cell dysfunction in the patho genesis of type 1 diabetes, factors other than impaired FPIR must also cont ribute to postprandial glucose tolerance in these subjects.