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Tst5.6
Testosterone (TRT) Research
Mostly mechanism / observationalLimited safety
9 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most Testosterone (TRT) studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality meta-analyses and randomised trials published 2010–2024 with a typical study size of 5,246 participants.
Based on 9 studies · 2 meta-analyses · 5 RCTs · 61,629 total participants
Confidence
High
By outcome
Sexual function & men's vitality
Mostly mechanism / observational9 studies
Safety profile
Mostly mechanism / observational4 studies
Heart & blood pressure
Mostly mechanism / observational3 studies
Bone health
Too few graded studies2 studies
Body composition & muscle
Too few graded studies1 study
Anemia & hematology
Too few graded studies1 study
Fertility & spermatogenesis
Too few graded studies1 study
Depression & mood
Too few graded studies1 study
Active research area
3 studies in the last 5 years · Latest meta-analysis: 2024
201020172024
1RCTn=790 · large study2016
Testosterone treatment for one year ... had a moderate benefit with respect to sexual function and some benefit with respect to mood and depressive symptoms but no benefit with respect to vitality or walking distance.
Snyder PJ, Bhasin S, Cunningham GR, Matsumoto AM, Stephens-Shields AJ, Cauley JA, et al.; Testosterone Trials Investigators. · The New England journal of medicine (2016)
The coordinated Testosterone Trials (TTrials) — seven randomized, double-blind, placebo-controlled trials in 790 men aged 65+ with confirmed low testosterone and symptoms, treated with testosterone gel for one year
Testosterone raised levels to the mid-normal range for young men and improved sexual activity, desire, and erectile function (the Sexual Function Trial), with smaller benefits in mood and depressive symptoms
No benefit for vitality or, separately, for cognitive function; walking-distance gains were small
In men with hypogonadism and preexisting or a high risk of cardiovascular disease, testosterone-replacement therapy was noninferior to placebo with respect to the incidence of major adverse cardiac events.
Lincoff AM, Bhasin S, Flevaris P, Mitchell LM, Basaria S, Boden WE, et al.; TRAVERSE Study Investigators. · The New England journal of medicine (2023)
TRAVERSE: a randomized, double-blind, placebo-controlled non-inferiority trial of transdermal testosterone in 5246 middle-aged and older hypogonadal men with high cardiovascular risk — the largest TRT cardiovascular-safety trial
Testosterone was non-inferior to placebo for major adverse cardiac events (cardiovascular death, nonfatal MI, nonfatal stroke), substantially reassuring the central safety question
However, atrial fibrillation, acute kidney injury, and pulmonary embolism were more frequent in the testosterone group
Testosterone is osteogenic, myogenic, and catabolic to fat ... testosterone therapy versus placebo on any primary outcome (bone density, muscle mass, fat mass, muscle strength/physical performance).
Buratto J, Kirk B, Phu S, Vogrin S, Duque G. · Endocrine practice (2023)
Systematic review and meta-analysis of 16 randomized placebo-controlled trials (1728 men, mean age 77) of testosterone therapy on musculoskeletal outcomes
Testosterone improved body composition — increased lean/muscle mass and reduced fat mass — consistent with its anabolic, fat-catabolic action
Effects on muscle strength and physical performance were more modest, and the review tracked adverse events alongside efficacy
Testosterone treatment for 1 year of older men with low testosterone significantly increased volumetric bone mineral density and estimated bone strength, more in trabecular than peripheral bone.
Snyder PJ, Kopperdahl DL, Stephens-Shields AJ, Ellenberg SS, Cauley JA, Ensrud KE, et al. · JAMA internal medicine (2017)
The TTrials Bone Trial — a randomized, placebo-controlled trial measuring volumetric BMD and finite-element-estimated bone strength by quantitative CT in older hypogonadal men
One year of testosterone significantly increased volumetric bone density and estimated strength, especially in trabecular (spine) bone
Provides the mechanistic bone-outcome anchor behind the body-composition/skeletal benefit
Testosterone treatment significantly increased the hemoglobin levels of older men with unexplained anemia as well as those with anemia from known causes.
Roy CN, Snyder PJ, Stephens-Shields AJ, Artz AS, Bhasin S, Cohen HJ, et al. · JAMA internal medicine (2017)
The TTrials Anemia Trial — a randomized, placebo-controlled trial of one year of testosterone in older hypogonadal men with anemia (both unexplained and from known causes)
Testosterone corrected anemia significantly more often than placebo, raising hemoglobin in both anemia subgroups
Establishes anemia correction as a genuine, randomized benefit of TRT in deficiency (consistent with testosterone's erythropoietic action)
Men with very low testosterone, higher LH, or very low estradiol concentrations had increased risk for all-cause mortality.
Yeap BB, Marriott RJ, Dwivedi G, Adams RJ, Antonio L, Ballantyne CM, et al. · Annals of internal medicine (2024)
Individual-participant-data meta-analysis pooling prospective cohorts of community-dwelling men to relate endogenous testosterone and related hormones to mortality and incident cardiovascular disease
Very low endogenous testosterone (and very low estradiol or higher LH) was associated with increased all-cause mortality — context for why deficiency matters
An observational/association analysis of endogenous hormone levels, NOT a trial of TRT — it does not show that giving testosterone reduces mortality
The trial was discontinued early because there was a significantly higher rate of cardiovascular adverse events in the testosterone group than in the placebo group.
Basaria S, Coviello AD, Travison TG, Storer TW, Farwell WR, Jette AM, et al. · The New England journal of medicine (2010)
Mandatory counter-evidence: the TOM (Testosterone in Older Men with Mobility Limitations) randomized, placebo-controlled trial in older men with limited mobility and a high burden of chronic disease
Stopped early because cardiovascular adverse events were significantly more frequent in the testosterone arm
Used a higher-dose gel regimen in a frail, comorbid population — the result that put TRT cardiovascular safety in question for over a decade
In all subjects, the post/pre-prescription rate ratio for testosterone prescription was 1.36 (1.03, 1.81) ... In men aged 65 years and older, the RR was 2.19.
Large cohort study (55,593 men) comparing non-fatal myocardial infarction rates in the 90 days after a first testosterone prescription with the prior year, benchmarked against PDE5-inhibitor users
Found an elevated rate of early non-fatal MI after starting testosterone, especially in men 65 and older and in younger men with prior heart disease
An observational signal (confounding by indication is possible), not a randomized result — but a real-world counter-signal that fueled the cardiovascular-safety debate
To achieve effective and reversible suppression of spermatogenesis, male hormonal contraception relies on suppression of testicular testosterone and sperm production using an androgen-progestin combination.
Thirumalai A, Page ST. · Annual review of medicine (2020)
Review of male hormonal contraception — directly documenting that exogenous androgens (testosterone) reliably and reversibly suppress spermatogenesis via HPTA suppression
The fertility-suppression that makes testosterone the backbone of experimental male contraceptives is the same effect that makes TRT a fertility hazard for men wanting children
Catalogs the associated side effects of androgen exposure — changes in libido, weight, hematocrit, and cholesterol