Glucose Disposal in Low-Birth-Weight Infants During Steady-State Hyperglycemia: Effects of Exogenous Insulin Administration

Abstract

The effects of exogenous insulin administration on glucose disposal during steady-state hyperglycemia were evaluated in eight well, low-birth-weight (LBW) infants (mean birth weight 1,090 gm; mean gestation 29 weeks) at age 5 to 14 days. The study was performed on two consecutive days. On the first day, at midpoint during a four-hour constant glucose infusion (14 mg/kg/min), a placebo was given. The following day, insulin (10 mU/kg/min) replaced the placebo. Serum insulin level increased significantly during steady-state hyperglycemia on both days. In contrast to placebo, the administration of exogenous insulin resulted in normoglycemia. It is speculated that the hyperglycemia during glucose infusion in well LBW infants is the result of persistent endogenous hepatic glucose production and/or decreased peripheral glucose utilization, both of which could be due to ineffective mediation of insulin on the liver or other insulin-sensitive peripheral tissues. The prompt reduction in serum glucose level which occurs as a result of the administration of exogenous insulin further suggests that in LBW infants a higher insulin level is necessary to achieve the appropriate control of glucose homeostasis. During this study, no osmotic diuresis was observed since the quantity of urinary glucose did not constitute an osmolar load.