Intravenous Glucose Tolerance in the Normal Newborn Infant: The Effects of a Double Dose of Glucose and Insulin

Abstract

The intravenous glucose tolerance test in normal vaginally delivered neonates, 3 to 6 hours old, is abnormal by adult standards. There is an initial slow rate of glucose disappearance from the blood comparable to that found in adult diabetics. After 60 to 70 minutes the rate increases. No rebound phenomenon is noted by 120 minutes after injection. Double glucose tolerance tests show that the rate of glucose disappearance in the initial phase is more rapid in the second test than in the first. It is comparable to the increased rate occurring 60-70 minutes after the first injection. Combined glucose-insulin tolerance tests show a rate of glucose disappearance in the first 60 minutes comparable to that found in normal adults after the injection of glucose alone. Intravenous glucose tolerance tests done on the third day of life show an increased rate of glucose disappearance as compared to the first hours of life, but this is still diminished as compared to the normal adult. On the basis of this data it is suggested that there is a diminished response of pancreatic insulin output to the stimulus of hyperglycemia during the early period of extra-uterine life and that this mechanism slowly improves over the first few days of life. A hypothesis is presented to explain the alterations in blood sugar observed in the newborn infant.