title: Growth hormone (GH) peak after falling asleep reflects spontaneous nocturnal GH secretion, however is not corresponding to the results of GH stimulating tests in children with short stature.
abstract: OBJECTIVE
  Growth hormone (GH) secretion is characterized by a pulsatile, circadian rhythm, with the highest concentrations at night hours. Evaluation of nocturnal GH secretion may be truncated to 6 hours. Growth hormone stimulating tests are the standard method of assessment of GH secretion. In Poland, the assessment of GH peak during 2 hours after falling asleep was introduced as a screening procedure in children, suspected for GH deficiency.  The aim of current study was to compare the results of a screening test with GH secretion during 6-hour nocturnal profile and with the results of GH stimulating tests, as well as with IGF-I secretion in children with short stature.
  
  
  METHODS
  In 72 short children, GH concentrations were measured every 30 minutes during first 6 hours after falling asleep and in two GH stimulating tests (the cut-off level of GH peak for all the tests was 10.0 ng/ml). Also, IGF-I concentrations were measured and expressed as IGF-I SDS for age and sex.
  
  
  RESULTS
  The screening test results correlated significantly with both GH peak in 6-hour profile and mean GH concentration, and the area under the curve (AUC) in 6 hour profile (r= 0.94, r=0.90 and r=0.89, respectively, p<0.05) but not with GH peak in stimulating tests (r=0.07, NS). There was no correlation between IGF-I secretion and any of the analyzed parameters of spontaneous and stimulated GH secretion.
  
  
  CONCLUSIONS
  The results of screening test seem to reflect overnight GH secretion in short children, remaining, however, discordant with the results of GH stimulating tests and with IGF-I secretion.
authors.affiliation: Department of Pediatric Endocrinology, Medical University of Lodz,, Poland. alewin@csk.umed.lodz.pl.
authors.forename: Joanna
authors.initials: J
authors.lastname: Smyczynska
authors.forename: Renata
authors.initials: R
authors.lastname: Stawerska
authors.forename: Andrzej
authors.initials: A
authors.lastname: Lewinski
authors.forename: Maciej
authors.initials: M
authors.lastname: Hilczer
mesh_terms: D002648:Child; D006130:Growth Disorders; D013006:Growth Hormone; D019382:Human Growth Hormone / Q000172:deficiency; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D012890:Sleep
chemical_list: D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone