Growth hormone--dependent growth failure.

Growth failure may be associated with low serum somatomedin concentrations despite normal to increased concentrations of serum growth hormone. We have recognized five patients who responded to GH administration with an increase in serum Sm and an acceleration in skeletal growth, and have characterized the circulating GH in an homologous human GH radioreceptor assay employing the IM-9 lymphocyte as a source of human GH receptor. These five prepubertal children, who had a mean height 7.8 SD below the mean for age, had a mean RIA-GH of 34.2 +/- 3.5 ng/ml in response to stimulation, a basal Sm activity by hypophysectomized rat cartilage bioassay of less than 0.3 IU/ml, and a mean peak Sm of 0.9 +/- 0.1 IU/ml in response to 48 hours of GH therapy. During a one-year trial of GH therapy, four of these children significantly increased their growth velocity as compared to their growth rate before GH therapy. These children had a mean RIA-GH/RRA-GH ratio of 2.f. The fifth patient had a low RIA-GH/RRA-GH ratio and had no increase in growth rate. These studies suggest that growth in certain growth retarded children may be dependent on exogenous GH, even though they are not GH deficient by standard criteria.