Activity of GH/IGF-1 axis in burn patients: comparison with normal subjects and patients with GH deficiency

The aim of this study was to clarify the activity of GH/IGF-1 axis as well as the variations of nutritional parameters following a thermal injury in man. To this goal, in 22 patients with burn [BURN, age (mean+/-SE): 46.5+/-3.4 yr, BMI: 25.0+/-0.8 kg/m2, % burn surface area: 26.0+/-3.0%, ROI score: 0.22+/-0.1] we evaluated IGF-1, IGF binding protein (IGFBP-3), GH, GH binding protein (GHBP), pre-albumin (pre-A), albumin (A) and transferrin (TRA) levels on days 1, 3, 7, 14 and 28 after intensive care unit (ICU) admission. IGF-1, IGFBP-3, GH and GHBP levels were also assayed basally in 29 normal subjects (Ns) (Ns, age: 47.5+/-2.8 yr, BMI: 22.0+/-1.4 kg/m2) and in 34 panhypopituitary patients with severe GH deficiency (GHD, age: 42.7+/-2.5 yr, BMI: 25.6+/-0.8 kg/m2). On ICU day 1, IGF-1 and IGFBP-3 in BURN were higher than those in GHD (p<0.05 for both, respectively) and lower than those in Ns (p<0.05) while GH levels in BURN did not differ from those in Ns and higher than GHD (p<0.01). In BURN, IGF-I and IGFBP-3 levels showed a progressive decline (p<0.05) with nadir on day 14, when they overlapped those in GHD, and then an increase on day 28, though persisting lower than in Ns, while GH levels did not vary during ICU stay. IGF-I levels were associated neither to burn extension nor to ROI score. On ICU day 1 pre-A, A and TRA levels were similar to those in Ns, but underwent a progressive decrease with nadir on day 7 (p<0.001) for pre-A and TRA, and later, on day 14 (p<0.05) for A; pre-A and TRA but not A showed a rebound increase (p<0.01) on day 14, though persistingly lower than in Ns. In conclusion, our present data firstly show the time course variation of IGF-I levels in burn patients as function of nutritional and hormonal variables. It has to be emphasized that in the most critical phase after burn injuries, IGF-1 levels are as low as in hypopituitary patients with severe GHD. The physiological basis which leads to the impairment of this endogenous anabolic drive in this phase is, however, not clear yet.