Objective: To gain insight into the effects of duration of type 2 diabetes on insulin secretion in patients with type 2 diabetes mellitus. Methods: C-peptide concentrations were measured every 2 years before and after intravenous injection of 1 mg of glucagon in 89 patients with type 2 diabetes (51 men and 38 women) as part of the Rochester Diabetic Neuropathy Study in those subjects who participated in follow-up (median, 12 years; range, 6 to 14). Results: Although insulin secretion decreased over time (P
