Demonstration of a dawn phenomenon in normal human volunteers.
Level 4 - case-series / case-control
Small observational physiological cohort with serial measurements in healthy volunteers
PubMed 6389230 · doi:10.2337/diab.33.12.1150
What was done
Eight healthy volunteers underwent serial blood sampling every 30 minutes between 1:00 a.m. and 9:00 a.m. Researchers measured plasma concentrations of glucose, insulin, C-peptide, and counterregulatory hormones (cortisol, epinephrine, norepinephrine, growth hormone, and glucagon). Rates of glucose production, glucose utilization, and insulin secretion were also determined across the overnight period.
What was found
After 5:30 a.m., plasma glucose, insulin, and C-peptide concentrations all increased significantly (P < 0.05). Rates of glucose production, glucose utilization, and insulin secretion similarly increased (P < 0.05). Plasma cortisol, epinephrine, and norepinephrine rose significantly from nocturnal nadirs between 4:00 and 6:30 a.m. Growth hormone increased episodically between 1:00 and 4:30 a.m. and then decreased by nearly 50% (P < 0.05). Glucagon levels did not change significantly. Exact baseline and peak numerical values for glucose and hormone concentrations were not provided in the abstract.
Why it matters
This study shows that the dawn phenomenon is a normal physiological circadian process driven by increased early-morning glucose production, suggesting that morning hyperglycemia in diabetes represents an exaggeration of normal physiology rather than an isolated disease-specific defect.
Limits
The study evaluated a very small cohort (n = 8). The abstract does not provide demographic details (such as age or sex) or absolute numerical values for the measured parameters. The observational timing cannot definitively confirm which specific counterregulatory hormone directly drives the rise in glucose production.
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