| Torben Leo Nielsen, Claus Hagen, Kristian Wraae, Lise Bathum, Rasmus Larsen, Egil Haug, Kim Brixen, Marianne Andersen
| | 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 | | Type | Conference paper [Abstract] | | Conference | The Endocrine Society's 89 th Annual Meeting | | Year | 2007 Month June | | Publisher | Endocrine Society | | Address | 8401 Connecticut Avenue, Suite 900, Chevy Chase, Maryland 20815-5817 | | Electronic version(s) | [pdf] | | BibTeX data | [bibtex] | | IMM Group(s) | Image Analysis & Computer Graphics |
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