@CONFERENCE\{IMM2007-05293,
    author       = "T. L. Nielsen and C. Hagen and K. Wraae and L. Bathum and R. Larsen and E. Haug and K. Brixen and M. Andersen",
    title        = "Contributions by the {CAG-}repeat Polymorphism of the Androgen Receptor Gene and Circulating Androgens to Muscle size. Odense Androgen Study – A population-based Study of 20-29 Year-old Danish Men.",
    year         = "2007",
    month        = "jun",
    booktitle    = "The Endocrine Society's 89 th Annual Meeting",
    volume       = "",
    series       = "",
    editor       = "",
    publisher    = "Endocrine Society",
    organization = "",
    address      = "8401 Connecticut Avenue, Suite 900, Chevy Chase, Maryland 20815-5817",
    url          = "http://www2.compute.dtu.dk/pubdb/pubs/5293-full.html",
    abstract     = "Context: The number of {CAG-}repeats within the {CAG-}repeat polymorphism of the androgen receptor gene is inversely correlated with the transcriptional activity mediated via the receptor.
Objective: To study the effect of {CAG-}repeat number and circulating androgens on muscle size, to examine {CAG-}repeat number in relation to body fat mass and circulating androgens, and to identify the best marker(s) of low muscle size amongst total testosterone (TT), bioavailable testosterone, and dihydrotestosterone.
Design, Setting, and Participants: Population-based study of 767 Danish men aged 20-29 years.
Main Outcome Measures: Thigh and axial muscle area, lower extremity, upper extremity, and trunk lean body mass (LBM), and total body fat mass (FM).
Results: {CAG-}repeat number correlated inversely with thigh and axial muscle area and with lower extremity {LBM}. These findings remained significant in multivariate analyses controlling for circulating androgens, physical activity, disease, and other covariates. {CAG-}repeat number also correlated positively with {FM} adjusted for weight, but not with the concentrations of any circulating androgens. {TT} and dihydrotestosterone correlated with all muscle outcomes. The prevalence of low muscle size increased exponentially with decreasing androgen levels and was almost tripled at {TT} levels <12.5 nmol/l.
Conclusion: The {CAG-}repeat polymorphism affects body composition in young men, independently of circulating androgens and other covariates: Fewer repeats are related with increased muscle size and reduced {FM,} while circulating androgens are unaffected. Both {TT} and dihydrotestosterone correlated with muscle size in a linear concentration-response relationship. {TT} was the best biomarker of low muscle size in young men.
Trial Registration: ClinicalTrials.gov: NCT00150163"
}