What testosterone level qualified men for the T-Trials?

Men needed two morning serum testosterone measurements below 275 ng/dL to enroll. This threshold is lower than the 300 ng/dL cutoff used by the AUA guideline, meaning the T-Trials studied men with clearly low levels, not borderline values.

Did testosterone improve energy levels in the T-Trials?

The primary vitality measure (FACIT-Fatigue) showed no statistically significant improvement. Some secondary vitality scales showed modest benefit, but the headline finding is that fatigue alone is not a strong reason to prescribe TRT based on this data.

How much did sexual function improve?

Sexual activity frequency roughly doubled in the testosterone group compared to placebo. Desire, erectile function, and overall sexual satisfaction all improved significantly. This was the most consistent and clinically meaningful benefit observed in the T-Trials.

Is testosterone gel safe for older men with heart disease?

The T-Trials excluded men with recent cardiovascular events. A coronary plaque sub-study raised concern about increased plaque volume. The larger TRAVERSE trial (2023) subsequently showed that TRT did not increase the rate of major cardiovascular events in men with or at high risk for CVD, providing some reassurance.

Did the T-Trials change FDA-approved indications for testosterone?

No. The FDA continues to restrict testosterone approval to men with hypogonadism from specific medical causes, not age-related decline. The T-Trials demonstrated symptomatic benefit in older men but did not alter regulatory labeling.

Do the T-Trials results apply to testosterone injections?

The trial used transdermal testosterone gel (AndroGel 1%) with dose titration to mid-normal levels. Injectable testosterone produces different pharmacokinetics, with higher peaks and lower troughs. While the mechanism of action is the same, direct extrapolation to injectables requires caution.

Did testosterone help bone density in the T-Trials?

Yes. The bone sub-study showed significant increases in volumetric bone mineral density and estimated bone strength. However, the trial was not powered to detect fracture reduction, so the clinical significance for fracture prevention remains uncertain.

How long should a man try TRT before deciding it works?

The T-Trials measured outcomes at 12 months. Sexual function improvements were apparent by 3 months and sustained through the trial. If a patient has not noticed meaningful improvement in his target symptoms by 6 to 12 months, the evidence does not support indefinite continuation.

What monitoring is needed during TRT based on T-Trials data?

The trial protocol included testosterone levels, hematocrit, PSA, and dose adjustments at months 1, 2, 3, 6, 9, and 12. Current AUA and Endocrine Society guidelines recommend similar monitoring schedules, with attention to polycythemia (hematocrit above 54%), PSA changes, and cardiovascular risk factors.

Can the T-Trials justify TRT for men in their 40s or 50s?

No. The trial enrolled only men 65 and older. Younger men have different symptom profiles, comorbidity burdens, and risk-benefit considerations. TRT in younger men may be reasonable for other clinical reasons, but the T-Trials do not provide direct evidence for that population.

What Testosterone Trials (T-Trials) Actually Changes in Clinical Practice

By HealthRX Medical Team

Published May 25, 2026Updated May 25, 2026Last reviewed May 25, 2026

At a glance

| Field | Detail | |---|---| | Trial name | Testosterone Trials (TTrials) | | N | 790 | | Population | Men ≥65 years with serum testosterone <275 ng/dL and symptoms | | Intervention | 1% testosterone gel (AndroGel), dose-titrated to mid-normal range | | Comparator | Matching placebo gel | | Duration | 12 months | | Primary endpoints | Sexual function (PDQ-Q4), vitality (FACIT-Fatigue), physical function (6-minute walk distance) | | Key result | Significant improvement in sexual function and 6-minute walk test; no significant vitality benefit on primary measure | | Registration | NCT00799617 |

Why This Trial Existed

Before 2016, testosterone prescribing in older men was running ahead of the evidence. Direct-to-consumer advertising had driven a surge in TRT prescriptions, particularly after 2000, yet no adequately powered RCT had tested whether raising testosterone levels in older men with age-related decline actually improved the symptoms that prompted treatment. Observational data pointed in several directions. The FDA had issued a safety communication in 2015 restricting approved indications to men with documented hypogonadism from identifiable causes, not simply low levels associated with aging. Clinicians needed a trial that measured what patients actually care about: sexual desire, energy, and the ability to walk without tiring.

The T-Trials were designed as seven coordinated sub-studies under a single enrollment umbrella. The three primary sub-studies (Sexual Function, Physical Function, Vitality) reported together in the 2016 NEJM publication. Four additional sub-studies (Cognitive Function, Anemia, Bone, Cardiovascular) reported subsequently, each extending the clinical picture.

What the Trial Actually Measured, and How

Enrollment Was Intentionally Narrow

Participants had to be 65 or older with two morning serum testosterone levels below 275 ng/dL and at least one qualifying symptom cluster: impaired sexual function, reduced physical function, or low vitality. This is a critical detail. The trial did not enroll men with borderline testosterone who felt fine. It enrolled men who were both biochemically low and symptomatic, a population that maps reasonably well to the men most clinicians would consider treating.

Exclusion criteria removed men with prostate cancer, PSA above 4 ng/mL, severe lower urinary tract symptoms (IPSS >19), recent cardiovascular events, or uncontrolled sleep apnea. These exclusions matter when translating results. The trial population was cleaner than most real-world TRT candidates.

Dose Titration Targeted a Specific Range

Testosterone gel was titrated to achieve serum levels in the mid-normal range for young men (targeting roughly 500 ng/dL). This is higher than some conservative protocols that aim for the low-normal range in older patients. The T-Trials protocol used AndroGel 1% with dose adjustments at months 1, 2, 3, 6, and 9. By month 3, the median testosterone in the treatment arm was approximately 470 ng/dL, compared to roughly 230 ng/dL in placebo. The separation was clean and sustained.

Outcome Measures Were Patient-Reported

The primary sexual function endpoint used the PDQ-Q4 (Psychosexual Daily Questionnaire, question 4), measuring sexual activity. Physical function used the 6-minute walk test. Vitality used the FACIT-Fatigue scale. All three are validated, patient-centered instruments, but they measure different things with different sensitivity thresholds.

The HealthRX Clinical Translation Framework

To assess what this trial should change in practice, we apply three filters: (1) Was the effect size clinically meaningful, not just statistically significant? (2) Does the trial population match your patient? (3) Have subsequent data confirmed or contradicted the finding?

Filter 1: Effect Sizes by Domain

| Domain | Measure | Treatment Effect | Statistical Significance | Clinically Meaningful? | |---|---|---|---|---| | Sexual function | PDQ-Q4 activity score | +0.58 vs +0.16 (placebo) | p <0.001 | Yes. Roughly doubled activity frequency. | | Sexual desire | DISF-M-II desire domain | Significant improvement | p <0.001 | Yes. Consistent with activity data. | | Physical function | 6-min walk distance | +14.3 m vs placebo | p = 0.05 | Borderline. Below the 20-30 m MCID used in cardiopulmonary rehab. | | Vitality | FACIT-Fatigue | No significant difference on primary | p = 0.36 | No. Secondary vitality measures showed modest benefit. |

Sexual function was the clear winner. The improvement was consistent across subgroup analyses and was accompanied by improvements in erectile function measured by IIEF. Physical function showed a statistically marginal gain that most rehabilitation specialists would consider below the threshold of clinical relevance. Vitality, the symptom that drives many men to seek TRT, showed no benefit on the pre-specified primary measure.

Filter 2: Does the Trial Population Match Your Patient?

The T-Trials enrolled a specific phenotype: men over 65, community-dwelling, with testosterone consistently below 275 ng/dL on two separate mornings, and with documented symptoms. This excludes several common clinical scenarios.

Men aged 40-64 with low testosterone. The trial says nothing about this population. Extrapolating from men 65+ to men in their 40s and 50s requires acknowledging different comorbidity profiles, different baseline sexual function trajectories, and different risk-benefit calculations for decades-long therapy.

Men with testosterone 275-400 ng/dL. The "low-normal" range was excluded. Many clinicians prescribe TRT to men in this range who report symptoms. The T-Trials provide no direct support for that practice.

Men with significant cardiovascular disease. The trial excluded recent MI, stroke, and unstable angina. The TRAVERSE trial (2023, NEJM) subsequently showed non-inferiority of TRT for major adverse cardiovascular events in men with or at high risk for CVD, partially filling this gap.

Filter 3: Subsequent Confirmatory or Contradictory Data

The T-Trials sub-studies that reported after the primary publication extended the picture in important ways.

Bone density (2017): Testosterone significantly increased volumetric BMD of the spine and estimated bone strength. This finding has not translated into fracture reduction data, but it supports skeletal benefit in men with very low testosterone.

Anemia (2017): Testosterone corrected unexplained anemia of aging in a meaningful proportion of men, with hemoglobin increases exceeding 1 g/dL in some participants. This is a genuinely underappreciated finding.

Cardiovascular (2018): Coronary artery plaque volume increased in the testosterone arm compared to placebo. This signal, measured by CT angiography, generated concern but was based on a small sub-study (n=170) and has been partially counterbalanced by the larger TRAVERSE cardiovascular safety data.

Cognitive function (2017): No improvement in cognitive function or memory. This effectively closes the door on TRT as a cognitive intervention in older men, a claim that had circulated in anti-aging medicine circles.

What Changed in Guidelines After T-Trials

The 2018 AUA guideline on testosterone deficiency incorporated T-Trials data directly, recommending that clinicians discuss the expected benefits and uncertainties of TRT with symptomatic men who have confirmed low testosterone on two morning samples. The AUA set 300 ng/dL as its diagnostic threshold, slightly above the T-Trials' 275 ng/dL cutoff.

The Endocrine Society's 2018 guideline similarly referenced the T-Trials, maintaining a recommendation against testosterone for age-related decline alone but acknowledging symptomatic benefit for men meeting biochemical criteria. Both guidelines emphasized shared decision-making, an approach that depends on clinicians accurately conveying what the T-Trials did and did not show.

The FDA's labeling for testosterone products continues to restrict the approved indication to men with conditions causing hypogonadism (genetic disorders, pituitary disease, chemotherapy), not age-related decline. The T-Trials did not change this regulatory posture. This creates a persistent gap between evidence-supported practice (symptomatic men over 65 with very low levels do benefit) and FDA-approved indications.

Limitations the Authors Acknowledged

The investigators were transparent about several constraints. The 12-month duration cannot address long-term safety, particularly prostate and cardiovascular risk over 5-10 years of continuous use. The sample size of 790 was powered for symptomatic endpoints, not for rare adverse events like thromboembolism or prostate cancer. The exclusively older (≥65) population limits generalizability to younger men. The use of transdermal gel means results may not apply directly to injectable formulations, which produce different pharmacokinetic profiles with higher peak levels.

The trial also had a notable dropout rate. Approximately 14% of participants in each arm did not complete 12 months. While balanced between groups, this level of attrition introduces uncertainty, particularly for the physical function and vitality endpoints where effect sizes were small.

What This Should Actually Change in Your Practice

Start with sexual function as the primary target. If a man over 65 presents with low libido, reduced sexual activity, and confirmed low testosterone, the T-Trials provide reasonable evidence that testosterone gel will help. If the primary complaint is fatigue alone, the evidence is weak.

Do not extrapolate to younger men without acknowledging the evidence gap. A 48-year-old with testosterone of 310 ng/dL and fatigue is not the T-Trials patient. Treatment may still be reasonable, but the supporting evidence comes from different (and weaker) study designs.

Set realistic expectations. Sexual function improved meaningfully. Walking distance improved marginally. Energy did not improve on the primary measure. Patients deserve to hear all three findings before starting therapy.

Monitor consistently. The T-Trials used a structured dose-titration protocol with regular lab monitoring. The coronary plaque signal, while not definitive, reinforces the need for cardiovascular risk assessment. The anemia sub-study suggests checking hemoglobin and hematocrit, both for benefit (correction of anemia) and risk (polycythemia).

Reassess at 12 months. The trial lasted one year. If a patient has not experienced meaningful symptomatic improvement by that point, continuing indefinitely is not supported by this data.

Frequently asked questions

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References

Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of Testosterone Treatment in Older Men. N Engl J Med. 2016;374(7):611-624. PubMed
Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). N Engl J Med. 2023;389(2):107-117. PubMed
Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol. 2018;200(2):423-432. PubMed
Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men with Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. PubMed
FDA Drug Safety Communication: Testosterone Products. FDA.gov