title: Influence of demographic factors and sport type on growth hormone-responsive markers in elite athletes.
abstract: BACKGROUND
  GH-responsive markers of the IGF system and of collagen turnover hold promise as the basis of a GH doping test.
  
  
  OBJECTIVE
  The purpose of this study was to determine the influence of age, gender, body mass index (BMI), ethnicity, and sporting type on GH-responsive serum markers in a large cohort of elite athletes from different ethnic backgrounds.
  
  
  METHODS
  The study was designed as a cross-sectional study.
  
  
  METHODS
  A total of 1103 elite athletes (699 males, 404 females), aged 22.2 +/- 5.2 yr, from 12 countries and 10 major sporting categories participated in this study.
  
  
  METHODS
  Serum IGF-I, IGF binding protein-3 (IGFBP-3), acid labile subunit (ALS), and collagen markers [N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (ICTP), N-terminal propeptide of type III procollagen (PIIINP)] were measured.
  
  
  RESULTS
  There was a significant negative correlation (r = -0.14 to -0.58, P < 0.0005) between age and each of the GH-responsive markers. Serum IGF-I, IGFBP-3, and ALS were all lower (P < 0.05), whereas the collagen markers PINP, ICTP, and PIIINP were higher (P < 0.05) in men than in women. Multiple regression analysis indicated that age, gender, BMI, and ethnicity accounted for 23-54% of total between-subject variability of the markers. Age and gender cumulatively accounted for 91% of the attributable variation of IGF-I and more than 80% for PINP, ICTP, and PIIINP. Gender exerted the greatest effect on ALS (48%), and BMI accounted for less than 12% attributable variation for all markers. The influence of ethnicity was greatest for IGFBP-3 and ALS; however, for the other markers, it accounted for less than 6% attributable variation. Analysis of 995 athletes indicated that sporting type contributed 5-19% of attributable variation.
  
  
  CONCLUSIONS
  Age and gender were major determinants of variability of GH-responsive markers except for IGFBP-3 and ALS. Ethnicity is unlikely to confound the validity of a GH doping test based on IGF-I and these collagen markers.
authors.affiliation: Garvan Institute of Medical Research and Department of Endocrinology, Darlinghurst, New South Wales 2010, Australia.
authors.forename: A E
authors.initials: AE
authors.lastname: Nelson
authors.forename: C J
authors.initials: CJ
authors.lastname: Howe
authors.forename: T V
authors.initials: TV
authors.lastname: Nguyen
authors.forename: K-C
authors.initials: KC
authors.lastname: Leung
authors.forename: G J
authors.initials: GJ
authors.lastname: Trout
authors.forename: M J
authors.initials: MJ
authors.lastname: Seibel
authors.forename: R C
authors.initials: RC
authors.lastname: Baxter
authors.forename: D J
authors.initials: DJ
authors.lastname: Handelsman
authors.forename: R
authors.initials: R
authors.lastname: Kazlauskas
authors.forename: K K
authors.initials: KK
authors.lastname: Ho
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D001798:Blood Proteins / Q000032:analysis* / Q000378:metabolism; D015992:Body Mass Index; D002352:Carrier Proteins / Q000097:blood; D024042:Collagen Type I; D003430:Cross-Sectional Studies; D003710:Demography; D005006:Ethnicity; D005260:Female; D006023:Glycoproteins / Q000097:blood; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D015999:Multivariate Analysis; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides; D011347:Procollagen / Q000097:blood; D012727:Sex Characteristics; D013177:Sports / Q000502:physiology*
chemical_list: D015415:Biomarkers; D001798:Blood Proteins; D002352:Carrier Proteins; D024042:Collagen Type I; D006023:Glycoproteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C075944:insulin-like growth factor binding protein, acid labile subunit; C047202:procollagen Type I N-terminal peptide; C041876:procollagen Type III-N-terminal peptide; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone