Pulsatile nature of growth hormone levels in critically ill trauma victims

Circulating growth hormone (GH) levels in normal persons fluctuate widely because of pulsatile GH secretion. It is not known whether this pulsatile nature and rhythmicity exist in severe injury. These data become necessary to decide the timing of supplementary GH administration for its optimal utilization. The purpose of this study was to investigate the GH circadian variation with respect to that of insulin-like growth factor-1 (IGF-1), insulin, C-peptide, and cortisol in the early flow phase of injury.

Plasma GH, IGF-1, insulin, C-peptide, and cortisol levels were measured at 1-hour intervals during 24 hours (8 AM to 8 AM) in 10 severely injured adults with multiple trauma during the early catabolic flow phase 24 to 48 hours after injury, when patients received maintenance fluids without calories or nitrogen.

The 24-hour integrated GH concentration is not different from either 12-hour mean diurnal or 12-hour mean nocturnal or mean 8 AM GH concentration. Pulsatile GH bursts persist in injured patients during both day and night. Pulsatile bursts do not exist for IGF-1, insulin, and C-peptide. The plasma levels of cortisol show time-dependent daily maximum and minimum levels.

Pulsatile GH bursts persist in injured patients but less frequently than seen in normal persons. The time of bolus administration of GH to augment the anabolic GH action in patients with trauma does not matter; however, for convenience morning administration may be preferable for patients in the intensive care unit.