title: Similar effects of long-term exogenous growth hormone (GH) on bone and muscle parameters: a pQCT study of GH-deficient and small-for-gestational-age (SGA) children.
abstract: OBJECTIVE
  Treatment with GH in short children has focused on height development. Little is known about the concomitant changes in muscle mass, bone structure and bone strength.
  
  
  METHODS
  Muscle area as well as parameters of bone architecture (bone mineral content, BMC; volumetric cortical density, total bone area, TBA; cortical area, cortical thickness, CT; and marrow area) were measured by means of pQCT (Stratec) at 65% of the proximal length of the forearm. The strength-strain index (SSI) was calculated as an indicator of bone strength.
  
  
  RESULTS
  Prepubertal children with GHD (mean values: age; 7.2 years; height SDS=-2.9 SDS; GH dose: 30 microg/kg/d) were followed at 0, 6, 12 (n=74) and 24 (n=55) months. Prepubertal children with SGA (mean values: age: 7.1 years; height SDS=-3.4 SDS; GH dose: 55 mug/kg/d) were followed at 0, 6, 12 (n=47) and 24 (n=35) months. Both groups showed a similar increase in height. At GH start, muscle mass and bone characteristics were lower than normal but similar in SGA vs. GHD. Muscle area (mean values, SDS) increased from -3.0 to -1.5 in SGA and from -2.4 to -1.0 in GHD. Bone geometry changed in a biphasic mode, with an increase in total bone area and lowering of bone mineral content (BMC) during the first 12 months, followed by an increase of BMC and CT thereafter. SSI (mean values, mm(3)) improved from 78 to 114 in GHD and from 62 to 101 in SGA after 24 months on GH. The increment in terms of SDS did not reach significance in SGA. SSI correlated positively with muscle area before and during GH treatment.
  
  
  CONCLUSIONS
  Bone strength and muscle mass are impaired in prepubertal children with GHD and SGA. Exogenous GH can indirectly improve bone structure and strength by inducing an increase in muscle mass. Our findings support the assumption that, in SGA, there is impaired tissue responsiveness to GH.
authors.affiliation: Paediatric Endocrinology Section, University Children's Hospital, Hoppe Seyler Strasse 1, D-72076, Tübingen, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Schweizer
authors.forename: David D
authors.initials: DD
authors.lastname: Martin
authors.forename: Martin
authors.initials: M
authors.lastname: Haase
authors.forename: Johannes
authors.initials: J
authors.lastname: Roth
authors.forename: Branko
authors.initials: B
authors.lastname: Trebar
authors.forename: Gerhard
authors.initials: G
authors.lastname: Binder
authors.forename: C Philipp
authors.initials: CP
authors.lastname: Schwarze
authors.forename: Michael B
authors.initials: MB
authors.lastname: Ranke
mesh_terms: D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000187:drug effects*; D002675:Child, Preschool; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage / Q000172:deficiency* / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000187:drug effects*; D011994:Recombinant Proteins / Q000627:therapeutic use; D014057:Tomography, X-Ray Computed