Absence of dawn phenomenon in normal children and adolescents

The dawn phenomenon consists of a rise in plasma glucose levels or insulin requirements in the early morning. This phenomenon has been observed in normal adults and in patients with diabetes mellitus. To determine whether this phenomenon also occurs in normal children and adolescents, we evaluated plasma glucose, insulin, C-peptide, and growth hormone levels during the early morning in 31 normal children between the ages of 8 and 18 yr. Blood samples were obtained through an indwelling catheter every 20 min for growth hormone and hourly for glucose, insulin, and C-peptide from 2100 to 0900 h. Glucose levels decreased slowly overnight from 2100 to 0900 h, despite increases in growth hormone levels. No significant rise in insulin or C-peptide levels was detected in the early morning in these normal subjects. There were no significant differences between prepubertal and pubertal children. We conclude that glucose, insulin, and C-peptide levels remain stable overnight, suggesting that the dawn phenomenon is not observed in normal children.