INSULIN-LIKE GROWTH-FACTOR-I, INSULIN-LIKE GROWTH-FACTOR BINDING-PROTEINS, AND GROWTH-HORMONE BINDING-PROTEIN IN SPANISH PREMATURE AND FULL-TERM NEWBORNS

The normal values of insulin-like growth factor I (ICF-I), IGF-binding proteins 1 and 3 (IGFBP-1 and IGFBP-3), and the high-affinity growth hormone binding protein (GHBP) are not well established in large serie s of healthy full-term newborns. We report the normative data for IGF- I, IGFBP-1, IGFBP-3, and GHBP in 271 normal Spanish full-term newborns , born between 37 and 42 weeks of gestation, and compare these results with the same parameters studied in 39 premature infants. Furthermore , we report the relationship between results found in the normal full- term newborns and those of 252 healthy prepubertal (Tanner stage I) Sp anish children. Serum GHBP, IGF-I, and IGFBP-3 levels are very low in the premature infant and show a significant increase in full-term newb orns and during childhood (p < 0.001; analysis of variance). In contra st, the serum IGFBP-1 levels are very high in premature newborns, fall in full-term newborns, and continue to decline during childhood (p < 0.001; analysis of variance). A positive correlation between GHBP, IGF -I, and IGFBP-3 versus gestational age was observed. In contrast, we f ound a negative correlation between IGFBP-1 and gestational age. There is a direct relationship between the ponderal index and IGF-I and IGF BP-3. When the group of premature newborns was divided into infants bo rn before or after 32 weeks of gestation, we found higher levels of IG F-I and IGFBP-3 (p < 0.01 and p < 0.05, respectively, by Student's t t est) in the group with the higher gestational age; however, the IGFBP- 1 level was lower in this group (p < 0.001 by Student's t test), with no differences seen in serum GHBP concentrations. The presence of IGFB Ps in the premature infant suggests that they are important modulators of IGF-I action during fetal growth and development.