title: Serum Sex Hormones, IGF-1, and IGFBP3 Exert a Sexually Dimorphic Effect on Lean Body Mass in Aging.
abstract: BACKGROUND
  Endogenous and exogenous sex hormones affect changes in body composition during aging via independent and dependent effects on the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis and associated binding proteins (BP).
  
  
  METHODS
  Fasting serum IGF-1, IGFBP3, testosterone, estrone, and sex hormone binding globulin were analyzed in 48 women on hormone replacement (HRT) (unopposed oral estrogen, HRT+, 74.0 +/- 6 years), 135 women not on HRT (HRT-, 77.3 +/- 7 years), and 128 healthy men (men, ). Total lean body mass (LBM) and total fat were measured by dual energy X-ray absorptiometry.
  
  
  RESULTS
  Total LBM decreased with age in all groups (p = .05). LBM was greater, and IGF-1, IGFBP3, and testosterone were lower in HRT+ versus HRT- women (p = .02, p = .01, p = .04, and, respectively). LBM in men was positively related to IGF-1 (p = .02) and testosterone (p < .01), whereas LBM was associated with IGFBP3 (p = .04) and total fat (p < .001) in female HRT+ and total fat (p < .01) in HRT- women. IGF-1 decreased with age in men and HRT- women (p < .01) but did not decrease in HRT+ women. Total fat significantly decreased across age (p < .05). Controlling for age and HRT, the rate of decrease in fat was slower in men versus women (p = .02). IGFBP3 decreased in all groups across age (p < .01), and the ratio of IGF-1 to IGFBP3 decreased faster in men compared to HRT+ and HRT- women (p = .02).
  
  
  CONCLUSIONS
  Our data indicate divergent influences of sex steroids, IGF-1, and IGFBP3 on age-related changes in LBM in healthy elderly men and women.
authors.affiliation: University of New Mexico-Health Sciences Center, Aging and Genetic Epidemiology Program, Albuquerque, 87131, USA.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Waters
authors.forename: C Lillian
authors.initials: CL
authors.lastname: Yau
authors.forename: George D
authors.initials: GD
authors.lastname: Montoya
authors.forename: Richard N
authors.initials: RN
authors.lastname: Baumgartner
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D015914:Estrogen Replacement Therapy; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D009929:Organ Size; D012727:Sex Characteristics; D013739:Testosterone / Q000097:blood
chemical_list: D012739:Gonadal Steroid Hormones; D018972:Insulin-Like Growth Factor Binding Protein 3; D013739:Testosterone; D007334:Insulin-Like Growth Factor I