Endogenous insulin secretion measured by C-peptide in maturity-onset diabetes controllable by diet alone.

Endogenous insulin secretion was quantified in patients with maturity-onset diabetes (MOD) whose diabetes was controllable solely by caloric regulation as primary therapy. Insulin was used adjunctively only and persistent attempts were made to withdraw it as weight loss occurred in response to diet. Insulin secretory capacity was measured by C-peptide response during a standard 100-g oral glucose tolerance test in 24 patients who achieved normalization of plasma glucose level as a result of dietary therapy alone. Summed C-peptide levels for the diet-controlled diabetic patients was 7.8 +/- 0.7 pmol/mL as compared with 6.1 +/- 0.45 pmol/mL for a group of ten normal-weight, nondiabetic volunteers.