Effect of Testosterone treatment on bone microarchitecture and bone mineral density in men: a two-year RCT.

Context Testosterone treatment increases bone mineral density (BMD) in hypogonadal men. Effects on bone microarchitecture, a determinant of fracture risk, are unknown. Objective Determine the effect of testosterone treatment on bone microarchitecture using high resolution-peripheral quantitative computed tomography (HR-pQCT). Design, setting, participants Men>50 years were recruited from six Australian centres. Interventions Injectable testosterone undecanoate or placebo over 2 years on the background of a community-based lifestyle program. Main outcomes Primary endpoint was cortical volumetric BMD (vBMD) at the distal tibia, measured using HR-pQCT in 177 men (one centre). Secondary endpoints included other HR-pQCT parameters and bone remodelling markers. Areal BMD (aBMD) was measured by dual energy X-ray absorptiometry (DXA) in 601 men (five centres). Using a linear mixed model for repeated measures, the mean adjusted differences (MAD) [95% CI] at 12 and 24 months between groups are reported as treatment effect. Results Over 24 months, testosterone treatment, compared to placebo, increased tibial cortical vBMD), 9.33mgHA/cm 3[3.96;14.71],p Conclusions In men>50 years, testosterone treatment for 2 years increased volumetric bone density, predominantly via effects on cortical bone. Implications for fracture risk reduction require further study.