Factors Determining the Plasma Insulin Response to Oral Glucose in Diabetes Mellitus

Oral glucose tolerance tests were performed and plasma insulin levels measured by immunoassay in sixty-four diabetic patients. Of the sixty-four, twenty-seven had mild or moderate and thirty-seven had severe carbohydrate intolerance. Of those with moderate diabetes, eleven (41 percent) showed a normal degree of insulin rise, but in eight this was delayed or prolonged. Seven patients (26 per cent) had an excessive insulin response, seven a flat response, and two a low rise with a delayed peak. Of the thirty-seven patients with severe diabetes, thirteen (35 per cent) had a normal degree of insulin rise, although this was prolonged or delayed in six. Only three patients (8 per cent) had an excessive response. Fourteen (38 per cent) had a flat response and seven (19 per cent) a low, delayed rise. Of ten ketotic patients studied, nine had a flat insulin response. Patients whose diabetes had been controlled either on diet or oral therapy, or on both, showed normal or excessive plasma insulin levels after oral glucose. Overweight subjects had higher plasma insulin levels than underweight subjects, but there was no correlation between the insulin levels and the degree of obesity. Mild carbohydrate intolerance was associated with a higher plasma insulin response than was severe carbohydrate intolerance.