URINARY INSULIN-LIKE GROWTH FACTOR-II EXCRETION IN HEALTHY INFANTS AND CHILDREN WITH NORMAL AND ABNORMAL GROWTH

The output of urinary IGF-II was measured by RIA in 12-h overnight uri ne samples obtained from 22 preterm and 15 full-term infants, 40 norma l children, 18 children with growth hormone (GH) deficiency, and 25 pa tients with idiopathic short stature. GH deficiency was defined as a p eak to GH provocative tests less-than-or-equal-to 9.9 mug/L during two provocative tests. The authenticity of urinary IGF-II was confirmed b y size exclusion chromatography. Statistical analysis was performed by one-way analysis of variance using the Student Neuman-Keuls test to d etect intergroup differences at the level of p < 0.05. The preterm and full-term infants excreted significantly higher amounts of urinary IG F-II (18.4 +/- 1.7 and 5.7 +/- 1.0 pmol/kg, respectively) compared wit h normal children (2.4 +/- 0.25 pmol/kg; p < 0.001). The output of uri nary IGF-II in preterm infants was greater than that observed in full- term infants (F = 84.7, p < 0.001). The control children excreted sign ificantly more IGF-II (2.4 +/- 0.2 pmol/kg) than children with GH defi ciency (0.9 +/- 0.1 pmol/kg) or idiopathic short stature (1.0 +/- 0.1 pmol/kg; F = 13.5; p < 0.001). Analysis of urinary IGF-II excretion ba sed on creatinine output yielded similar results. Data on urinary IGF- I and GH previously published were correlated and compared with the ex cretion pattern of urinary IGF-II. Urinary GH correlates with urinary IGF-II in groups 3, 4, and 5 (0.58 and 0.46 per body weight and nmol o f creatinine, respectively; p < 0.01), as well as in the preterm and f ull-term infants (0.51, p < 0.01; 0.54, p < 0.01) when the data were s tandardized for kg of body weight and nmol of creatinine, respectively . Children with GH deficiency excrete significantly less IGF-II compar ed with control subjects. This pattern is similar to that of urinary I GF-I. The highest urinary IGF-II output is observed in preterm infants , possibly reflecting a period of persistent elevation of IGF-II secon dary to the young gestational age of these infants.