AI-generated research brief — verify at source
TRT Improves Lipid and Vascular Markers but Raises Arrhythmia Concern in Older Men
A meta-analysis of 31 randomised controlled trials found that testosterone replacement therapy (TRT) significantly reduced LDL cholesterol by approximately 6.6 mg/dL (WMD: −6.64 mg/dL, 95% CI: −8.65 to −4.63) and improved ischemic and vascular markers, while also revealing an approximately 58% higher odds of arrhythmia compared with placebo (OR: 1.58, 95% CI: 1.21–2.05). The overall cardiovascular risk picture is therefore mixed, with meaningful benefits to several surrogate endpoints offset by a potentially important safety signal whose clinical implications remain unresolved.
What Was Studied
This meta-analysis examined the cardiovascular safety of TRT in middle-aged and older men with low or low-normal testosterone levels, a population for whom TRT is an established treatment for hypogonadism. The assessment covered a broad range of outcomes, including lipid profiles, markers of myocardial ischemia, vascular structure, and nonfatal cardiovascular events, to determine whether TRT confers net cardiovascular benefit or harm in this group.
How It Was Studied
Researchers conducted a systematic review and meta-analysis, searching PubMed, Web of Science, EMBASE, and the Cochrane Library for randomised controlled trials published up to July 2024. Thirty-one RCTs involving a total of 9,437 middle-aged and older men with low or low-normal testosterone were eligible for inclusion, with all trials comparing TRT against placebo. Treatment durations across the included trials ranged widely, from as short as 40 days to as long as 36 months, introducing considerable variability in the duration of follow-up. The analysis was conducted in accordance with Cochrane Handbook guidance (version 6.0) and was prospectively registered with PROSPERO.
What Was Observed
- Lipid improvements across multiple fractions: TRT was associated with statistically significant reductions in total cholesterol (approximately 10.2 mg/dL lower; WMD: −10.20, 95% CI: −14.52 to −5.88), triglycerides (approximately 7.0 mg/dL lower; WMD: −7.03, 95% CI: −12.25 to −1.81), and LDL cholesterol (approximately 6.6 mg/dL lower; WMD: −6.64, 95% CI: −8.65 to −4.63). HDL cholesterol showed no statistically significant change (WMD: −1.39, 95% CI: −3.12 to 0.35), suggesting TRT does not substantially erode the protective lipoprotein fraction.
- Improved exercise ischemic threshold: Across trials of single-dose to 14-week duration, TRT significantly extended the time to onset of 1-mm ST-segment depression during treadmill testing by approximately 67 seconds (WMD: +67.37 s, 95% CI: 55.05–79.69), indicating a meaningful reduction in exercise-induced myocardial ischemia during the treatment period.
- Reduction in carotid intima-media thickness: Over longer treatment periods of 12 to 36 months, TRT was associated with a statistically significant reduction in carotid intima-media thickness of approximately 0.03 mm (WMD: −0.03, 95% CI: −0.05 to −0.02), a structural vascular marker commonly used as a surrogate for atherosclerotic progression.
- Arrhythmia safety signal: Among 6,598 participants assessed for nonfatal cardiovascular events, TRT was associated with approximately 58% higher odds of arrhythmia compared with placebo (OR: 1.58, 95% CI: 1.21–2.05). This signal was statistically robust, though whether it translates into meaningful clinical harm requires further investigation.
Why This Matters
TRT is widely prescribed for hypogonadism, yet its cardiovascular safety profile has been a persistent source of clinical uncertainty. This pooled analysis of 31 RCTs offers the most comprehensive randomised evidence assembled to date on TRT’s effects across multiple cardiovascular surrogate endpoints simultaneously. The identification of a consistent arrhythmia signal — alongside lipid and vascular benefits — raises questions about the net cardiac risk-benefit balance that prescribers and researchers will need to address through dedicated mechanistic and longer-term outcome studies.
How to Read This Result
While the meta-analytic evidence base is drawn from randomised trials and is considered high quality, the wide variation in treatment durations, heterogeneous trial populations, and the uncertain clinical significance of the arrhythmia signal collectively mean that these findings should be interpreted as informative but not definitive, particularly for long-term cardiovascular risk assessment.
Limitations
Treatment durations ranged from 40 days to 36 months across included trials, which substantially limits the ability to draw conclusions about long-term cardiovascular outcomes. The clinical meaning of the observed arrhythmia signal — whether it represents a transient pharmacological effect or a durable risk — remains uncertain and is not resolved by the current data. Additionally, heterogeneity in participant characteristics and trial designs across the 31 RCTs may reduce the comparability of pooled estimates and the generalisability of results to specific patient subgroups.