Growth hormone secretory profiles: variation on consecutive nights

Area of Science:

• Pediatric Endocrinology
• Reproductive Endocrinology
• Clinical Chemistry

Background:

• Overnight growth hormone (GH) testing is crucial for diagnosing short stature.
• Reproducibility of GH testing is essential for accurate clinical interpretation.
• The impact of common daytime medications on overnight GH secretion requires clarification.

Purpose of the Study:

• To assess the reproducibility of 12-hour overnight GH profiles in short children.
• To determine the effect of daytime levodopa and clonidine administration on overnight GH secretion.
• To evaluate the clinical implications of GH testing variability.

Main Methods:

• Consecutive 12-hour overnight GH profiles were analyzed in 48 short children (ages 5-16).
• GH stimulation testing with levodopa and clonidine was administered during the day.
• Night-to-night changes in pooled GH concentrations and peak GH levels were quantified.

Main Results:

• Significant night-to-night variations in overnight pooled GH concentrations were observed in 12% of subjects (>100% increase).
• In the remaining subjects, night-to-night changes ranged from -60% to +88%.
• Daytime levodopa and clonidine administration showed no discernible effect on overnight GH secretion.

Conclusions:

• Overnight GH testing exhibits considerable night-to-night variability in short children.
• The results suggest that a single overnight GH profile may not accurately reflect normal physiological GH secretion.
• Confirmation of GH test results is recommended to ensure clinical validity, advising caution in interpreting single-test outcomes.