title: Growth hormone is positively associated with surrogate markers of bone turnover during puberty.
abstract: BACKGROUND
  Puberty is characterized by increases in growth hormone (GH) and insulin-like growth factor-1 (IGF-1) and the pubertal growth spurt. Bone formation and resorption also increase, consistent with increased bone metabolism.
  
  
  OBJECTIVE
  To determine the relationship between pubertal bone metabolism, GH and IGF-1. We hypothesized that bone turnover peaks at the time of greatest pubertal GH secretion.
  
  
  METHODS
  Subjects included 86 girls and boys, 9-17 years-old (BMI 10th-90th percentiles). Because higher endogenous GH secretion is associated with a higher nadir following oral glucose, we used the GH nadir following a 2-h OGTT as indicative of GH status. Fasting serum IGF-1, aminoterminal propeptide of type 1 procollagen (P1NP) and carboxy-terminal collagen crosslinks (CTX) were obtained. Subjects were grouped per expected timing of peak growth. Group 1: Tanner 1 girls and Tanner 1-2 boys (period preceding peak growth), Group 2: Tanner 2-3 girls and Tanner 3-4 boys (period of peak growth) and Group 3: Tanner 4-5 girls and Tanner 5 boys (period following peak growth).
  
  
  RESULTS
  GH peaked at mid-puberty (Group 2) and IGF-1 in late puberty (Group 3). P1NP and CTX were highest in mid-puberty compared with early and late puberty (P = 0·0009 and 0·006 in girls and P = 0·005 and 0·04 in boys). GH, but not IGF-1, correlated with P1NP (r = 0·46 in both genders, P ≤ 0·008) and CTX (r = 0·37 and 0·38, P = 0·04 and 0·02 in girls and boys, respectively). Similarly, on regression modelling, GH (but not IGF-1) predicted both bone turnover markers in both genders.
  
  
  CONCLUSIONS
  GH is strongly associated with pubertal bone metabolism, independent of systemic IGF-1 in girls and boys.
authors.affiliation: Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Russell
authors.forename: Anne
authors.initials: A
authors.lastname: Breggia
authors.forename: Nara
authors.initials: N
authors.lastname: Mendes
authors.forename: Anne
authors.initials: A
authors.lastname: Klibanski
authors.forename: Madhusmita
authors.initials: M
authors.lastname: Misra
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000097:blood* / Q000378:metabolism*; D001842:Bone and Bones / Q000378:metabolism*; D002648:Child; D024042:Collagen Type I / Q000097:blood; D005260:Female; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000097:blood; D011347:Procollagen / Q000097:blood; D011627:Puberty / Q000097:blood*
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C047202:procollagen Type I N-terminal peptide; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I