Insulin deficiency in non-insulin-dependent diabetics

In this study, the prevalence of severe insulin deprivation amongst 104 non-insulin-dependent diabetes mellitus (NIDDM) patients was determined using a mixed meal pancreatic stimulation test (2.4 MJ). Of the 104 patients, 62 were recently diagnosed and 42 had been diabetic for between 1 and 40 years, but were not adequately controlled on diet and oral hypoglycaemic agents. Twenty-one (34%) of the recently diagnosed patients and 13 (31%) of the poorly controlled patients had peak post-testmeal insulin responses less than 160 pmol/l (less than 23 mU/l)--values 3 SD below normal--and were therefore considered to have severe blunting of beta cell response to nutrient secretagogues. Amongst recently diagnosed diabetics, these patients, as a group, had higher blood glucose levels (P less than 0.05) and lower body weights (P less than 0.01) but overall these parameters correlated poorly with insulin responses. Islet cell antibodies were positive in only one patient, whereas they were present in three others with less severe insulin secretory defects. For the treated diabetics, insulin release showed very low non-significant correlations with duration of diabetes, age, weight and glycaemic control. Islet cell antibodies were present in five patients, one only showing peak insulin values less than 160 pmol/l. These data suggest that about one-third of new diabetics and one-third of treated diabetics with poor glycaemic control are insulin deficient. Clinical and biochemical parameters, including islet cell antibodies, appear to be of no value in identifying this sub-group requiring insulin therapy. Their early recognition is best facilitated by routine pancreatic function tests.