INSULIN-LIKE GROWTH-FACTOR-I (IGP-I) AND IGF-BINDING PROTEIN-3 CONCENTRATIONS COMPARED TO STIMULATED AND NIGHT GROWTH-HORMONE IN THE EVALUATION OF SHORT CHILDREN - A CLINICAL RESEARCH-CENTER STUDY

To evaluate the relative usefulness of insulin-like growth factor I (I GF-I) and IGF-binding protein-3 (IGFBP-3) in screening for GH status, GH stimulation (arginine-insulin/L-DOPA) tests and overnight GH studie s (every 20 min sampling) were performed in 104 healthy short children (32 girls), aged 3-16 yr (height, -1.8 or more SD). IGFBP-3 had no ad vantage over IGF-I in screening sensitivity or specificity. IGF-I corr elated with mean nighttime GH. Both IGF-I and IGFBP-3 correlated with peak stimulated GH. To identify more than 90% of children with GH defi ciency (GHD) and borderline GHD, the mean values for age for IGF-I and IGFBP-3 were required as the cut-off criterion. However, at this crit erion, 70% or more of idiopathic short stature (ISS) children would ha ve to undergo testing to identify 90% of GHD or borderline GHD. More s tringent criteria (-1.0, -1.64, and -2.0 SD) were more specific, but l ost sensitivity. A practical application is suggested. Screening use o f IGF-I with criterion of -1.0 SD would identify a subgroup that inclu des 88% of GHD, 71% of borderline GHD, and 46% of ISS. Both IGF-I and IGFBP-3 higher than -1.0 SD would accurately identify 68% of ISS as no t needing GH testing. Evaluation of growth velocity would identify the remaining children requiring definitive testing. Thus, combined scree ning for GHD using both IGF-I and IGFBP-3 has no better sensitivity th an either test alone. However, such combined screening will improve th e specificity and thus decrease the number of normal but short childre n who might otherwise undergo unnecessary testing.