INSULIN-LIKE GROWTH FACTOR-I BLOOD-LEVELS IN SEVERELY BURNED PATIENTS- EFFECTS OF TIME POST INJURY, AGE OF PATIENT AND SEVERITY OF BURN

OBJECTIVES Insulin-like growth factor-I (IGF-I) is a polypeptide growt h factor that stimulates protein synthesis. The aims of this study wer e to determine (1) the effect of a severe burn on blood IGF-I levels a nd (2) the variables controlling IGF-I level variations during recover y of these hypermetabolic patients. PATIENTS Eleven patients, nine men and two women (age range 22-55 years) were studied for 25 days follow ing a severe burn (18-75% of total body surface area, mean 36%). Nitro gen balances were recorded daily and total IGF-I levels were measured every 3 days. MEASUREMENTS IGF-I was extracted from serum using a vali dated formic acid-acetone methodology, then measured by a double antib ody radioimmunoassay. IGF-I levels were compared to those of a referen ce healthy population. RESULTS Within 24 hours following injury, IGF-I levels were low in all patients when compared to normal values for th e same age range (mean +/- SEM of all patients, 131 +/- 26 mug/l). The y remained low for the first week (days 4 and 7, 109 +/- 16 mug/l), th en increased to reach normal values at the end of the study period (da ys 10-16, 144 +/- 19 mug/l, P = 0.005 when compared to days 4-7; days 19-25, 206 +/- 30 mug/l, P = 0.008 when compared to days 10-16). IGF-I levels were negatively correlated with age in the second phase of rec overy only (days 10-16, r = - 0.70, P < 0.05; days 19-25, r = - 0.75, P < 0.01) and with severity of burn between days 19 and 25 (r = - 0.62 , P < 0.05). The presence of bronchial burn injury tended to lower IGF -I blood concentration (P = 0.08). Whereas IGF-I concentrations increa sed in the later phase of recovery, nitrogen balances did not. As a re sult, there was no significant correlation between these parameters. C ONCLUSIONS IGF-I levels followed a biphasic pattern in severely burned patients. They dropped dramatically in response to the traumatic shoc k, then increased during recovery. The degree of increase was dependen t on the age of the patient and on the severity of the burn, but was n ot associated with an improvement in the nitrogen balance.