Serum IRI in insulin-treated diabetics during a 24-hour period.

Serum immunoreactive insulin extracted with acid ethanol (total IRI) and blood glucose were measured in two groups of diabetics and a control group during 24-hour periods. One group of diabetics had received insulin for less than 1 month, and none had yet developed insulin antibodies. The other had been treated with insulin for 2 years or more. The average level of total IRI in the diabetics without antibodies was similar to that in the normals, but highly elevated in diabetics with antibodies, although the blood glucose levels were similar in the two diabetic groups. The increase in total IRI after the insulin injections was more rapid in patients receiving quick-acting insulin and most pronounced in those with the highest levels of total IRI. The total IRI peaked in the afternoon and dropped during the night. The short-term insulin-treated patients showed a better degree of diabetes control than those treated for 2 years or more. No correlation was found however, between the total IRI level and the degree of control in the latter group. The patients with the highest levels of total IRI had the highest frequency of hypoglycemic episodes. This is in agreement with the concept that the insulin antibodies may function as a circulating depot, which releases insulin irrespective of the metabolic need.