Serum levels of true insulin, C-peptide and proinsulin in peripheral blood of patients with cirrhosis.

The levels of proinsulin, immunoreactive insulin, true insulin (calculated from the difference, namely immunoreactive insulin-proinsulin) and C-peptide were determined in the fasting state and during a 3-h oral glucose tolerance test after administration of 100 g of glucose in 12 patients with cirrhosis with normal oral glucose tolerance test (50 g) and in 12 healthy subjects serving as controls. In the patients with cirrhosis the serum levels of proinsulin and immunoreactive insulin were significantly higher in the fasting state and after glucose loading than in the healthy subjects. The serum level of true insulin was also higher in the patients with cirrhosis, but the difference was less pronounced and only significant at a few of the time points. The serum level of C-peptide was very similar in both groups. These results emphasize that cirrhosis is a condition in which the serum proinsulin level is raised and that this hyperproinsulinaemia contributes greatly to the increased immunoreactive insulin levels observed in patients with this disease.