Growth hormone and somatomedin A in girls with adolescent idiopathic scoliosis.

Girls with adolescent idiopathic scoliosis are taller than nonscoliotic girls of the same age. This observation may be related to factors regulating longitudinal growth. Plasma growth hormone was determined in a group of scoliotic girls by double antibody radioimmunoassay under the following conditions: 1) Insulin induced hypoglycemia, 2) glucose tolerance test, 3) exercise. Somatomedin A was determined by a method based on the ability of serum to stimulate the incorporation of radioactive sulphate in embryonic chick cartilage. The results were compared with those obtained in a control group of healthy nonscoliotic girls of comparable age. After overnight fasting and after at least one hour's rest the basal growth hormone level was 9.8+/-11.1 (+/-S.D.) ng/ml in the scoliotic girls (n=48) and 2.2+/-1.1 ng/ml in the controls (n=15). This difference is significant. In the hypoglycemia test the peak growth hormone level tended to be higher in the scoliotic girls but the difference is not significant. In the exercise test the maximal value was reached at different times in the two groups: at 20 min after start of the exercise in the scoliotic girls (n=14, 17.3+/-11.8 ng/ml) and at 40 min in the controls (n=9, 16.0+/-6.6 ng/ml). In the glucose tolerance test the growth hormone level was suppressed in both groups but the mean values tended to be higher during the first 120 min in the scoliotic girls. The serum somatomedin levels were higher in the group of scoliotic girls (n=19, 1.13+/-0.17 U/ml) than in the controls (n=14, 0.88+/-0.16 U/ml) and the difference is significant. The results obtained are difficult to interpret but suggest that growth hormone secretion is higher in girls with adolescent idiopathic scoliosis than in healthy girls of comparable age.