Correlative study of radioreceptor assay and radioimmunoassay of serum growth hormone in children: normal children and HGH-treated pituitary dwarfs.

A sensitive and reproducible radioreceptor assay (RRA) for human growth hormone (HGH) is described. It allows the evaluation of HGH concentrations as low as 2 ng/ml. It has a limited cross-reactivity with human prolactin, which does not interfere at physiological levels in children. Comparison of the results with those of radioimmunoassay (RIA) showed no discrepancies in the serum of normal children before and after stimulation tests for GH (mean RRA/RIA ratio 1.03 +/- SEM 0.04, range 0.75 to 1.65) nor in the serum from hypopituitary dwarfs during the 12 h following an im injection of 6 mg of HGH (mean RRA/RIA ratio 1.05 +/- 0.04, range 0.84 to 1.28). It is concluded that receptoractivity of HGH is parallel to its immunoreactivity in normal children and in hypopituitary patients clinical grade HGH.