The KID Study V: the natural history of type 2 diabetes in younger patients still practising a profession. Heterogeneity of basal and reactive C-peptide levels in relation to BMI, duration of disease, age and HbA1.

In a detailed evaluation of the data accumulated for 493 type 2 diabetics who participated in the KID Study, pre- and postprandial C-peptide was correlated with blood glucose level. HbA 1 , body mass index (BMI), duration of disease and age. As described earlier the KID-Study examined a younger cohort of type 2 diabetics predominately practising a profession. Our investigations demonstrate a significant increase of pre- as well as postprandial C-peptide levels with increasing obesity. However, delta C-peptide, as an indicator at the reaction capacity of pancreatic secretion, decreases significantly and continuously. Pre- as well as postprandial C-peptide levels decrease significantly with up to 15-20 years duration of disease. The preprandial pancreatic secretion is usually even at a high normal level at such a late stage whereas the secretory reserve of normal or mildly overweight as well as of obese type 2 diabetics is more impaired. In contrast to patients with a BMI 30 will also develop impairment of basal insulin secretion over decades. The patient's age did not influence the pre- or postprandial insulin secretion. The quality of metabolic control as measured by the HbA 1 has nearly exclusive impact on the secretory reserve capacity. Correlation with increasing HbA 1 concentrations, the postprandial but not the preprandial C-peptide levels decreased significantly and continuously. Predictive factors for a deterioration in pancreatic function are in order of importance: the extent of obesity, the quality of metabolic control and only last the duration of diabetes. Fortunately, consistent diabetic care can have an impact on the first two.