REDUCED CONCENTRATION OF SERUM GROWTH HORMONE-BINDING PROTEIN IN CHILDREN WITH IDIOPATHIC SHORT STATURE

One possible explanation for the growth failure in children with idiopathic short stature (ISS) is reduced peripheral responsiveness to GH. In Laron syndrome, growth retardation is caused by GH resistance due to GH receptor (GH-R) defects, which are associated in most cases with absent or low serum concentrations of the GH-R-related GH-binding protein (GHBP). We tested the hypothesis that some children with ISS have reduced serum concentrations of GHBP and that this may reflect decreased sensitivity to GH. A ligand-mediated immunofunctional assay was used to measure biochemically active GHBP in serum from 1549 children, including 773 controls, 573 with ISS, 107 with GH deficiency (GHD), and 96 with Turner syndrome (TS). Ages ranged from 1-17 yr. Serum GHBP concentrations in children with GHD, ISS, and TS were converted to so scores and compared to controls by analysis of variance. In male and female ISS subjects, approximately 90% had GHBP concentrations below the age- and sex-adjusted mean for controls, and 20% had GHBP concentrations below the normal range. The mean serum GHBP so score was lower in both males and females with GHD (-0.6) or ISS (-1.2) than in controls (both P < 0.005). The mean for ISS males was significantly lower than that for GHD males (P < 0.0001). The mean GHBP so score for girls with TS (-0.3) did not differ significantly from that of the control females. The decreased levels of serum GHBP in some children with idiopathic short stature suggest that these children could have a defect at the level of the GH-R.