Exogenous somatostatin raises plasma insulin levels in patients with insulin-dependent diabetes mellitus

The effect of cyclic somatostatin on circulating insulin levels was studied in eight patients with insulin-dependent diabetes mellitus (IDDM). The study was performed after an overnight fast when their subcutaneous depots of insulin had been depleted during i.v. insulin substitution for 18 hours. A constant rate i.v. insulin infusion (0.4 mU/kg/min) was given for 240 min and somatostatin was co-infused between 60-120 min (100 micrograms/h) and 180-240 min (250 micrograms/h) respectively. Plasma insulin, blood glucose and hematocrit were measured at 15 min intervals. Hematocrit fell from 41.7 to 38.3% during the study period. Somatostatin increased the plasma insulin levels, corrected for the changes of hematocrit, by approximately 8% in the low dose (P less than 0.05) as well as in the high dose (P less than 0.05) period. It is concluded that somatostatin interferes with the clearance of insulin thereby increasing the circulating plasma insulin levels in IDDM patients without residual insulin secretion.