title: Influence of body mass index and gender on growth hormone (GH) responses to GH-releasing hormone plus arginine and insulin tolerance tests.
abstract: The aim of this study is to assess whether gender and body mass index (BMI) should be considered in developing thresholds to define GH deficiency, using GH responses to GHRH + arginine (ARG) stimulation and insulin tolerance test (ITT). Thirty-nine healthy subjects (19 males, 20 females; ages 21-50 yr) underwent GHRH + ARG, and another 27 subjects (19 males, 8 females; ages 20-49 yr) underwent ITT. Peak GH response was significantly higher (P = 0.005) after GHRH + ARG than with ITT, and this difference could not be explained by age, gender, or BMI. Peak GH response was negatively correlated with BMI in both tests (GHRH + ARG, r = -0.76; and ITT, r = -0.65). Peak GH response to GHRH + ARG was higher in females than males (P = 0.004; ratio = 2.4), but it was attenuated after eliminating the influence of BMI (P = 0.13; ratio = 1.6). No significant gender differences were found in peak GH responses to ITT, which could be due to the smaller number of female subjects studied. GH response to GHRH + ARG and ITT stimulation is sensitive to BMI differences and less so to gender differences. A higher BMI is associated with a depressed GH response to both stimulation tests. BMI should therefore be considered as a factor when defining the diagnostic cut-off points in the assessment of GH deficiency, whereas whether gender should be likewise used is inconclusive from this study.
authors.affiliation: General Clinical Research Center, Harbor-University of California Los Angeles (UCLA) Medical Center, 1000 West Carson Street, Torrance, California 90509, USA.
authors.forename: Xiao-Dan
authors.initials: XD
authors.lastname: Qu
authors.forename: Irene T
authors.initials: IT
authors.lastname: Gaw Gonzalo
authors.forename: Mohammed Y
authors.initials: MY
authors.lastname: Al Sayed
authors.forename: Pejman
authors.initials: P
authors.lastname: Cohan
authors.forename: Peter D
authors.initials: PD
authors.lastname: Christenson
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Swerdloff
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Kelly
authors.forename: Christina
authors.initials: C
authors.lastname: Wang
mesh_terms: D000328:Adult; D001120:Arginine; D015992:Body Mass Index; D003940:Diagnostic Techniques, Endocrine; D005260:Female; D019382:Human Growth Hormone / Q000097:blood / Q000172:deficiency*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D008297:Male; D008659:Metabolic Diseases / Q000175:diagnosis*; D008875:Middle Aged; D009842:Oligopeptides; D012727:Sex Characteristics
chemical_list: D007328:Insulin; D009842:Oligopeptides; D019382:Human Growth Hormone; C041048:growth hormone releasing hexapeptide; D001120:Arginine