Plasma somatomedin activity measured as thymidine factor in normal children with average and constitutionally tall stature

The plasma thymidine activity determined as ³H-thymidine incorporation into lectin-activated normal human lymphocytes was studied in 20 normal children and 37 with constitutionally tall stature. No significant difference was demonstrated between the two groups. In both groups, thymidine activity is higher after age 10 and the difference is significant when thymidine activity is related to bone age. In both groups, thymidine activity was correlated with bone age (r = 0.572, p <0.001).