Insulin secretory response in Japanese type 2 (non-insulin-dependent) diabetic patients.

Insulin (immunoreactive insulin, IRI) response during a 100 g oral glucose tolerance test was studied in a large number of patients with definite diabetes, equivocal diabetes, and other pathological states causing glucose intolerance. Definite diabetes was diagnosed in patients with overt fasting hyperglycemia. Once the diagnosis of definite diabetes was made, IRI response remained low after improvement of glucose tolerance. Glucose intolerance caused by other pathological extra-pancreatic conditions was usually accompanied by increased IRI response. IRI response in equivocal diabetes was variable, but almost always decreased in those who developed definite diabetes later. In subjects with a strong family history of type 2 diabetes, the prevalence of a low IRI response was high. In non-diabetic subjects, weight gain caused a marked increase in IRI response and a small increase in blood glucose, while in those who developed diabetes, IRI increased little despite the marked increase in blood glucose. These data suggest that low IRI response is an important feature of type 2 diabetes, perhaps with a hereditary basis in part. It precedes the occurrence of overt hyperglycemia and persists after improvement of glucose tolerance.