title: Serum collagen crosslinks as markers of bone turn-over during GH replacement therapy in growth hormone deficient adults.
abstract: OBJECTIVE
  Bone metabolism is an important target for GH replacement therapy. However, in adults, treatment periods exceeding 12 months are required for a positive effect of GH on bone mineral density. Thus, to detect an early effect of GH on bone, markers of bone turn-over are important. Pyridinoline (PYR) and deoxypyridinoline (DPYR) are well-defined sensitive markers of bone resorption, but to date only urinary assays have been available. We report the use of a novel assay to measure changes in serum PYR and DPYR in GH deficient (GHD) adults during GH replacement therapy.
  
  
  METHODS
  The study consisted of a 6-month randomized, double-blind, placebo-controlled study of the administration of GH (Genotropin) (0.25 IU/Kg/week (0.125 IU/kg/week for the first four weeks)) followed by a 6-month open phase of GH therapy.
  
  
  METHODS
  Thirty-five GHD adults (17 women; mean age 39.8 years; range 21.1-59.9) on conventional hormone replacement therapy as required, were studied.
  
  
  METHODS
  Bone formation was analysed using serum bone alkaline phosphatase (BAP) and serum osteocalcin (OC). Bone resorption was analysed using serum pyridinoline (PYR) and serum deoxypyridinoline (DPYR). Bone mineral density (BMD) was determined by dual energy X-ray absorptiometry (DEXA).
  
  
  RESULTS
  After 6 months placebo treatment there were no significant changes in any of the bone markers analysed, nor in BMD. In the active arm of the study there was a significant increase in serum OC, BAP, PYR and DPYR (P = 0.03, P = 0.004, P = 0.003 and P = 0.01, respectively), remaining significantly elevated over their baseline levels for the subsequent 6 months of treatment (P = 0.04, P = 0.009, P = 0.003 and P = 0.04, respectively). No changes were observed in BMD in any of the groups after 6 months GH treatment. In the active arm of the study, after 12 months GH treatment there was a significant increase in BMD at both the lumbar spine and femoral neck (P = 0.01 for both sites).
  
  
  CONCLUSIONS
  In summary, the present study confirms that administration of GH treatment to GHD adult patients significantly activates bone remodelling, with the effect of GH both in bone formation and bone resorption markers being maximal after 6 months of treatment. The serum assay for PYR and DPYR has a number of practical and theoretical advantages over the urine assay and gave similar results to those previously reported for the urine assay.
authors.affiliation: Department of Endocrinology, St Bartholowmew's Hospital, London, UK.
authors.forename: J
authors.initials: J
authors.lastname: Rodríguez-Arnao
authors.forename: I
authors.initials: I
authors.lastname: James
authors.forename: A
authors.initials: A
authors.lastname: Jabbar
authors.forename: P J
authors.initials: PJ
authors.lastname: Trainer
authors.forename: D
authors.initials: D
authors.lastname: Perrett
authors.forename: G M
authors.initials: GM
authors.lastname: Besser
authors.forename: R J
authors.initials: RJ
authors.lastname: Ross
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D000596:Amino Acids / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D015519:Bone Density; D001849:Bone Diseases, Endocrine / Q000097:blood / Q000188:drug therapy* / Q000503:physiopathology; D016723:Bone Remodeling / Q000187:drug effects*; D002851:Chromatography, High Pressure Liquid; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D013006:Growth Hormone / Q000172:deficiency*; D019382:Human Growth Hormone / Q000627:therapeutic use; D006801:Humans; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D015675:Osteocalcin; D019382:Human Growth Hormone; C015484:pyridinoline; D013006:Growth Hormone; C036020:deoxypyridinoline; D000469:Alkaline Phosphatase