RADIOIMMUNOASSAY OF INSULIN IN PLASMA AND URINE IN OBESE SUBJECTS AND IN DIABETIC PATIENTS

Abstract

ABSTRACT By the use of the double antibody method the immunologically demonstrable insulin, both in the plasma and urine of obese subjects without clinically manifest diabetes and in diabetics who had not been treated with insulin has been determined. In obese subjects without clinically manifest diabetes, hyperinsulinism was found both in the fasting state and during the glucose tolerance tests. In these subjects the 24-hour urinary excretion of insulin was significantly higher than in that of normal subjects. In obese diabetics the mean fasting plasma insulin concentration was found to be significantly higher than in normal subjects, but during oral glucose tolerance tests, despite marked hyperglycaemia, the increase in the mean plasma insulin concentration was only of the same order as in that of normal subjects and had a maximum that was reached later. The 24-hour urinary excretion of insulin in obese diabetics was of the same order as in that of normal subjects. In non-obese diabetics the mean fasting plasma insulin concentration was lower than in normal subjects and lowest in the poorest regulated diabetics with high fasting blood sugar and ketonuria. During glucose tolerance tests it was not possible to demonstrate any increase in the plasma insulin concentration in the non-obese diabetics with ketonuria, while in non-obese diabetics without ketonuria a slight increase in the plasma insulin concentration was found during glucose tolerance tests. The 24-hour urinary excretion of insulin was reduced in relation to the excretion in normal subjects. Thus, the investigations have shown that hyperinsulinism should be regarded as a characteristic of obesity per se, while the clinically manifest diabetes is always connected with hypoinsulinism in relation to body weight.