title: Androgens may mediate a relative preservation of IGF-I levels in overweight and obese women despite reduced growth hormone secretion.
abstract: BACKGROUND
  Obesity is characterized by reduced GH secretion, but data regarding IGF-I levels and their determinants are conflicting.
  
  
  OBJECTIVE
  The objectives were to determine whether IGF-I levels are reduced and to investigate determinants of GH and IGF-I in healthy overweight and obese women.
  
  
  METHODS
  A cross-sectional study was performed.
  
  
  METHODS
  The study was conducted at a General Clinical Research Center.
  
  
  METHODS
  Thirty-four healthy women without pituitary/hypothalamic disease participated, including 11 lean [body mass index (BMI) <25 kg/m(2)], 12 overweight (BMI > or =25 kg/m(2) and <30 kg/m(2)), and 11 obese (BMI > or =30 kg/m(2)) women of comparable age (overall mean age, 30.7 +/- 7.8 yr).
  
  
  METHODS
  There was no intervention.
  
  
  METHODS
  The main outcome measures were frequent sampling (every 10 min for 24 h) for GH, peak GH after GHRH-arginine stimulation, IGF-I, IGF binding protein-3, estrone, estradiol, testosterone, free testosterone, SHBG, homeostasis model assessment of insulin resistance, and abdominal fat.
  
  
  RESULTS
  Mean 24-h GH and peak stimulated GH were lower in overweight than lean women and lowest in obese women. Mean IGF-I levels trended lower in obese, but not overweight, compared with lean women. Free testosterone was positively associated with IGF-I (R = 0.36, P = 0.04) but not with GH measures. Visceral fat was the only determinant of mean 24-h GH (R(2) = 0.66, P < 0.0001) and of peak stimulated GH (R(2) = 0.63, P < 0.0001), and mean 24-h GH accounted for 39% of the variability of IGF-I (P = 0.0002), with an additional 28% (P < 0.0001) attributable to free testosterone levels.
  
  
  CONCLUSIONS
  Despite a linear decrease in GH secretion and peak stimulated GH levels with increasing BMI in healthy overweight and obese women, IGF-I levels were not commensurately reduced. Androgens may contribute to this relative preservation of IGF-I secretion in overweight and obese women despite reduced GH secretion.
authors.affiliation: Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Utz
authors.forename: A
authors.initials: A
authors.lastname: Yamamoto
authors.forename: P
authors.initials: P
authors.lastname: Sluss
authors.forename: J
authors.initials: J
authors.lastname: Breu
authors.forename: K K
authors.initials: KK
authors.lastname: Miller
mesh_terms: D000328:Adult; D000728:Androgens / Q000097:blood / Q000502:physiology*; D015992:Body Mass Index; D002940:Circadian Rhythm / Q000502:physiology; D003430:Cross-Sectional Studies; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009765:Obesity / Q000097:blood / Q000378:metabolism*; D050177:Overweight / Q000097:blood / Q000378:metabolism*; D012738:Sex Hormone-Binding Globulin / Q000032:analysis / Q000378:metabolism
chemical_list: D000728:Androgens; D012739:Gonadal Steroid Hormones; D012738:Sex Hormone-Binding Globulin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I