title: Seasonality of growth response to GH therapy in prepubertal children with idiopathic growth hormone deficiency.
abstract: OBJECTIVE
  Longitudinal growth of children exhibits seasonal variation. In both healthy children and in children with growth hormone (GH) deficiency (GHD) receiving GH therapy, growth rate is maximal during spring and summer. In the present study, we analyzed the growth response to GH therapy in children with GHD as a function of the season when therapy was started.
  
  
  METHODS
  Anthropometric measurements and biochemical analyses of GH secretion status and bone formation were longitudinally assessed in a cohort of 52 prepubertal children with GHD (14 girls, mean age 7.6 years) who were treated with a fixed dose of GH (0.025 mg/kg/day).
  
  
  RESULTS
  Auxological assessments over the 2-year observation period revealed a significantly better growth response to GH therapy in children who started therapy between the spring and summer (group 1) compared with children who started in the autumn or winter (group 2). The difference was largest in the initial 3-month treatment period (35%; P<0.01). The initial better gain in height of group 1 was sustained during the study period. Baseline peak GH levels during stimulation tests and insuin-like growth factor-I levels did not differ between the two groups. However, group 1 had significantly higher bone resorption and formation markers, either at the start or shortly after initiation of GH treatment. This suggests that children with GHD have higher bone turnover during spring and early summer, irrespective of GH therapy.
  
  
  CONCLUSIONS
  In summary, this study suggests that the season of GH initiation is a determinant of the initial growth response to GH replacement in prepubertal children with GHD.
authors.affiliation: Children's Hospital, University of Cologne, Joseph-Stelzmann-Strasse 9, D-50924 Cologne, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Land
authors.forename: W F
authors.initials: WF
authors.lastname: Blum
authors.forename: A
authors.initials: A
authors.lastname: Stabrey
authors.forename: E
authors.initials: E
authors.lastname: Schoenau
mesh_terms: D015415:Biomarkers / Q000097:blood / Q000652:urine; D001846:Bone Development / Q000187:drug effects*; D001862:Bone Resorption / Q000188:drug therapy; D002648:Child; D015331:Cohort Studies; D005260:Female; D006130:Growth Disorders / Q000188:drug therapy*; D019382:Human Growth Hormone / Q000008:administration & dosage* / Q000172:deficiency; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012621:Seasons
chemical_list: D015415:Biomarkers; D019382:Human Growth Hormone