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B O D Y   P R O P O R T I O N S   I N   S M A L L   F O R   G E S T A T I O N A L   A G E   C H I L D R E N   A F T E R   R E C E I V I N G   G R O W T H   H O R M O N E   T R E A T M E N T     Introduction   The  common  definition  of  small  for  gestational  age  (SGA)  children  refers  to  a  birth   weight  below  the  10th  percentile  for  gestational  age1.  Researchers  suggest  that  low   birth  weight  followed  by  rapid  weight  gain  during  early  postnatal  life  is  associated   with  long-­‐term  risks  for  central  obesity,  insulin  resistance  and  cardiovascular  dis-­‐ eases,   known   as   the   metabolic   syndrome2,3.   Other   studies   indicate   that   not   only   accelerated4,  but  also  decelerated5  weight  gain  in  these  infants  is  associated  with  a   risk  on  the  metabolic  syndrome.  Therefore,  an  accurate  follow  up  of  the  growth  of   SGA   children   is   necessary   and   should   be   performed   by   a   physician   known   with   consequences  of  abnormal  growth  in  childhood.  This  is  even  more  important  realiz-­‐ ing  that  growth  velocity  in  SGA  children  is  different  from  normal  weight  children.  In   SGA   children,   both   weight   and   length   remain   behind   during   their   first   year   of   life   but  thereafter  most  children  show  a  catch-­‐up  growth  in  weight  beyond  the  normal   range   for   non-­‐SGA   children,   which   can   be   partly   explained   by   a   regression   to   the   mean.   However,   a   large   part   of   the   SGA   children   show   faster   acceleration   in   their   weight   gain   compared   to   their   length   which   discrepancy   is   estimated   as   an   extra   risk  factor  for  overweight  at  the  age  of  5  years6.       Those   children   who   do   not   correct   their   length   spontaneously   are   eligible   for   treatment   with   recombinant   human   growth   hormone   (rhGH).   Treatment   with   rhGH   based   on   the   indication   criteria   reviewed   by   the   Dutch   Growth   Research   Foundation7,  is  an  effective  and  safe  approach  to  reduce  the  adult  height  deficit  that   short   SGA   children   otherwise   face8.   In   GHD   children   it   is   shown   that   besides   its   positive  effect  on  growth,  rhGH  also  influences  metabolism9,10.  The  basal  metabolic   rate  increases11,  visible  as  a  change  in  body  composition  by  an  increase  in  fat-­‐free   mass  (FFM)12.  rhGH  treatment  of  SGA  children  also  results  in  a  decline  in  fat  mass   (FM)   and   an   increase   in   FFM,   which   is   consistent   with   the   lipolytic   and   anabolic   properties  of  rhGH  treatment13.  In  a  study  of  Hoos  et  al  the  change  in  body  compo-­‐ sition   in   GHD   children   was   already   detectable   after   6   weeks   of   treatment   with   rhGH14 as  measured  by  total  body  water  (TBW)  with  the  Deuterium  dilution  meth-­‐ od.  A  nationwide  study  revealed  that  treatment  with  rhGH  changes  the  body  com-­‐ position  in  SGA  children  too,  but  less  compared  to  GHD  children15.  This  can  be  pos-­‐ sibly   explained   because   SGA   children   have   a   reduced   body   fat   percentage   before   treatment   with   rhGH   in   contrast   to   GHD   children   whose   body   fat   percentage   is   increased16,17.  In  addition  SGA  children  have  a  reduced  sensitivity  for  IGF-­‐1  (insu-­‐ lin-­‐like   growth   factor   1)   unlike   GHD   children18.   Therefore,   in   SGA   children,   a   decrease  in  FM  can  hardly  be  expected  and  mainly  an  increase  in  FFM  can  be  meas-­‐ ured.  Although  the  Deuterium  method  is  accepted  as  a  golden  standard  to  measure   TBW,  in  SGA  children  it  seems  therefore  less  accurate  to  estimate  the  effect  of  rhGH   treatment.       61  


Proefschrift binnenwerk Manon Ernst_DEF.indd
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