title: Evidence of insulin-like growth factor binding protein-3 proteolysis during growth hormone stimulation testing.
abstract: OBJECTIVE
  The ternary complex is composed of insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3 and acid labile subunit (ALS). Growth hormone (GH) promotes IGFBP-3 proteolysis to release free IGF-I, ALS, and IGFBP-3 fragments. Our aim was to determine whether elevated GH levels during GH stimulation testing would trigger IGFBP-3 proteolysis.
  
  
  METHODS
  This prospective study of 10 short prepubertal children (height standard deviation score -2.37 +/- 0.31) used arginine and GH releasing hormone stimulation to study dynamic changes in the ternary complex moieties. IGFBP-3 was measured in two assays: a radioimmunoassay (RIA) that detects both cleaved and intact IGFBP-3; and an immunochemiluminescence assay (ICMA) that detects only intact IGFBP-3.
  
  
  RESULTS
  IGFBP-3 measured by RIA increased by 19% (p < 0.05), while IGFBP-3 measured by ICMA did not significantly increase (6.1%).
  
  
  CONCLUSIONS
  The significant increase in IGFBP-3 measured by RIA, but not ICMA, provides evidence of IGFBP-3 proteolysis during acute GH stimulation.
authors.affiliation: Division of Endocrinology, Department of Pediatrics, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, MA 01655, USA. benjamin.nwosu@umassmemorial.org
authors.forename: Benjamin U
authors.initials: BU
authors.lastname: Nwosu
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Soyka
authors.forename: Amanda
authors.initials: A
authors.lastname: Angelescu
authors.forename: Mary M
authors.initials: MM
authors.lastname: Lee
mesh_terms: D001120:Arginine / Q000097:blood; D002648:Child; D004392:Dwarfism / Q000188:drug therapy* / Q000378:metabolism; D005260:Female; D013007:Growth Hormone-Releasing Hormone / Q000627:therapeutic use*; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D008297:Male; D011446:Prospective Studies; D011627:Puberty
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D019382:Human Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D001120:Arginine