EFFICACY OF INSULIN-LIKE GROWTH-FACTOR BINDING-PROTEIN-3 IN PREDICTING THE GROWTH-HORMONE RESPONSE TO PROVOCATIVE TESTING IN CHILDREN TREATED WITH CRANIAL IRRADIATION

Recent data suggest that the plasma concentration of insulin-like grow th factor binding protein 3 (IGFBP-3) is useful as a screening test fo r growth hormone (GH) deficiency In this study, we measured by radioim munoassay the levels of IGFBP-3 in a group of 20 subjects (12 males) o f 5 years and 7 months to 16 years of age undergoing standard GH testi ng following cranial irradiation. The patients had received 1800 to > 6000 cGy of radiation to the hypothalamic-pituitary region, a median o f 2.7 years (range 2-7 years) prior to testing. The IGFBP-3 concentrat ions were discordant with the results of GH testing 60% (12/20) of the time. Although IGFBP-3 levels were below the mean for age in 14 of 15 GH-deficient (peak GH <10 mu g/I) patients, only three of 15 GH-defic ient patients had IGFBP-3 concentrations that fell below age-adjusted norms. In contrast, the IGFBP-3 levels were within the normal range in all five patients with normal GH responses. The low sensitivity (20%) of IGFBP-3 in predicting the subjects with abnormal responses was not improved by adjusting the values for bone age or stage of puberty. We conclude that a single plasma determination of IGFBP-3 is not a usefu l screening test for GH deficiency among patients previously treated w ith cranial irradiation.