Lack of association between androgen receptor polymorphisms and bone mineral density or physical function in older men

Individuals whose androgen receptors have short polyglutamine tracts (resulting from CAG repeats) may have greater receptor signaling activity of the androgen receptor. We evaluated the association between bone mineral density (BMD) and CAG repeats in 91 older men with normal (control) and low femoral neck (EN) BMD (OP) or a history of femoral fracture (FX). Bioavailable testosterone (BioT) and physical performance, including composite score (EPESE) and physical activity (PASE), were also measured. Comparing FX, OP, and control subjects, we observed BMD Tscores of -2.16 +/- 1.08, -2.26 +/- 0.74, and -0.20 +/- 0.40 (p < 0.001); CAG repeat lengths of 21.9 +/- 2.7, 22.5 +/- 2.4, and 22.3 +/- 2.9 (p = 0.63); BioT levels of 2.29 +/- 1.25, 2.19 +/- 1.11, and 3.99 +/- 1.25 nmol/L (p < 0.001); EPESE scores of 8.0 +/- 3.0, 9.7 +/- 2.0, and 11.3 +/- 0.9 (p < 0.001); and PASE scores of 91 +/- 66, 122 +/- 66, and 200 +/- 55 (p < 0.001), respectively. There were no significant correlations between CAG repeats and BioT or physical performance. Men with osteoporosis or fracture had lower BioT, physical performance, and physical activity than controls. This study found no association between CA G repeats and FN BMD in older men with normal or low BMD or FX.