Serum Sex Hormones, IGF-1, and IGFBP3 Exert a Sexually Dimorphic Effect on Lean Body Mass in Aging.
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.
Waters
Debra L
DL
University of New Mexico-Health Sciences Center, Aging and Genetic Epidemiology Program, Albuquerque, 87131, USA.
Yau
C Lillian
CL
Montoya
George D
GD
Baumgartner
Richard N
RN
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
D012739:Gonadal Steroid Hormones; D018972:Insulin-Like Growth Factor Binding Protein 3; D013739:Testosterone; D007334:Insulin-Like Growth Factor I