Plasma somatomedin activity after injury in man and its relationship to other hormonal and metabolic changes.

Plasma somatomedin activity was measured in 12 patients who had sustained non-fatal musculo-skeletal injuries. It was depressed for 2-3 d after injury, but this depression bore no relationship to the catabolic response to injury which, as judged by urinary nitrogen excretion, was maximal at about one week. The depression of somatomedin activity may have been related to the high plasma cortisol concentrations observed during the first few days after injury. Plasma growth hormone concentrations were high acutely after injury but rapidly returned to normal. The changes in plasma somatomedin activity were thus unrelated to those in growth hormone, but were very similar to those in plasma insulin concentrations. A marked positive relationship was observed between plasma insulin concentrations and urinary nitrogen excretion, indicating unresponsiveness of protein metabolism to the normal anabolic effects of insulin. The study showed, however, that this was not as a result of low somatomedin activity.