Effects of testosterone on body composition, bone metabolism and serum lipid profile in middle-aged men: a meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 16117815 · doi:10.1111/j.1365-2265.2005.02339.x
What was done
A systematic review and random-effects meta-analysis evaluated 29 randomized controlled trials investigating testosterone administration versus control in middle-aged and older men. Data were abstracted from MEDLINE, Cochrane Library, EMBASE, and Current Contents databases by two independent reviewers. The analysis pooled 1,083 participants (625 randomized to testosterone, 427 to placebo, and 31 to observation; weighted mean age 64.5 years, range 49.9–77.6; mean baseline testosterone 10.9 nmol/l). Outcomes evaluated included body composition, muscle strength, bone mineral density, bone metabolism markers, and serum lipid profiles.
What was found
Testosterone administration reduced total body fat by 1.6 kg (CI: 0.6 to 2.5), representing a -6.2% change (CI: -9.2% to -3.3%), and increased fat-free mass by 1.6 kg (CI: 0.6 to 2.6), or +2.7% (CI: 1.1% to 4.4%), with no change in body weight. Muscle strength findings were heterogeneous, with a non-significant trend toward improvement in knee/leg extension and dominant handgrip (standardized mean difference [SMD] = 0.3, CI: -0.0 to 0.6). Lumbar spine bone mineral density increased by +3.7% compared with placebo (CI: 1.0% to 6.4%), with no effect at the femoral neck, while bone resorption markers decreased (SMD = -0.6, CI: -1.0 to -0.2). Total cholesterol decreased by 0.23 mmol/l (CI: -0.37 to -0.10) without changing LDL cholesterol, and HDL cholesterol fell only in studies with higher baseline testosterone levels (-0.085 mmol/l, CI: -0.017 to -0.003).
Why it matters
This meta-analysis quantifies the average physiological effects of testosterone replacement in aging men, confirming benefits for lean mass, adiposity, and lumbar bone density. It also highlights that functional strength benefits remain inconsistent and that lipid changes depend on baseline androgen levels and drug formulation.
Limits
The included trials were small (averaging under 40 subjects per study), and the abstract notes significant heterogeneity across studies driven by variable testosterone doses, formulations, and aromatization capacity. Clinical outcomes such as fracture incidence, mobility events, and long-term cardiovascular risks were not reported.
Cited by
- supports Exogenous testosterone and androgen administration lowers and suppresses HDL cholesterol levels.