title: Serum levels of insulin-like growth factor I (IGF-I) and IGF binding protein 3 reflect spontaneous growth hormone secretion.
abstract: The relationship between 24-h GH secretion, insulin-like growth factor (IGF) I serum levels, IGF-binding protein 3 (IGFBP-3) levels and height was studied in 114 healthy children and adolescents (147 tests). A significant correlation was found between the spontaneous GH secretion expressed as the area under the curve above baseline (AUCb) or the calculated 24-h GH secretion rate (GHb) and IGF-I (n = 147, r = 0.65, or 0.78, respectively, P < 0.001) or IGFBP-3 levels (r = 0.48 or 0.62, P < 0.001). Correlations were also significant within the various subgroups [females (n = 51), males (n = 96), prepubertal children (n = 75), pubertal children (n = 72)]. The slopes of the regression lines of IGF-I levels vs. AUCb or GHb were clearly steeper in pubertal children than in prepubertal ones; this was not as evident with IGFBP-3. In prepubertal children, a significant correlation was found between height (compared to Swedish reference values) standard deviation scores (SDS) and IGF-I SDS (n = 75, r = 0.66, P < 0.001) or IGFBP-3 SDS (r = 0.61, P < 0.001). The reproducibility during repeated testing (19 individuals, 6 prepubertal) was best with IGFBP-3 as compared to AUCb, GHb, or IGF-I which showed considerable variability. The data suggest: 1) that IGF-I and IGFBP-3 serum levels reflect spontaneous GH secretion in healthy individuals; 2) IGF-I levels are more sensitive to GH regulation than IGFBP-3; 3) in puberty, there may be increased sensitivity of IGF-I regulation by GH as compared to the prepubertal stage; 4) short children have low IGF-I and IGFBP-3 levels, whereas tall children have high levels, a fact which is likely to contribute to the understanding of height variability in a healthy population; 5) the good reproducibility of IGFBP-3 on repeated testing makes it an interesting parameter for the evaluation of the GH-IGF-axis. IGFBP-3 measurements may substitute for GH profiles in many cases, when the goal is an estimation of the GH secretion rate.
authors.affiliation: University Children's Hospital Tübingen, Germany.
authors.forename: W F
authors.initials: WF
authors.lastname: Blum
authors.forename: K
authors.initials: K
authors.lastname: Albertsson-Wikland
authors.forename: S
authors.initials: S
authors.lastname: Rosberg
authors.forename: M B
authors.initials: MB
authors.lastname: Ranke
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000097:blood / Q000502:physiology; D001827:Body Height; D002352:Carrier Proteins / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007223:Infant; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D015203:Reproducibility of Results
chemical_list: D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone