High levels of testosterone in the blood have been linked to a greater risk of coronary artery disease in men, according to a new study from researchers at the University of Cambridge.
When there is a medical need to boost testosterone, the benefits are likely to outweigh the risks, but this might not necessarily be the case when taken to boost performance
Emily Morbey
The findings could have implications for the use of testosterone supplements, which while they have approved medical applications, are increasing in popularity, particularly among younger men who see testosterone as a way to fight ageing, enhancing performance or building strength.
Testosterone supplementation is an approved treatment for hypogonadism, a condition in which the body doesn't make enough of the hormone, and which typically manifests with fatigue and sexual dysfunction. Evidence from randomised controlled trials has shown beneficial effects of testosterone supplementation on sexual function, lean mass and muscle strength. Low circulating testosterone - that is, testosterone in the blood - is also a risk factor for poor metabolic health.
Recent years have seen testosterone supplements being promoted increasingly on social media and by influencers, often aimed towards younger men to boost their testosterone levels for perceived benefits like muscle growth, strength, energy, and confidence.
However, questions remain about the long-term health impacts of testosterone levels.
Observational studies have linked low measured testosterone levels with an increased risk of coronary artery disease in men, but randomized controlled trials - the 'gold standard' for testing the effectiveness of treatments - have been inconclusive and often contradictory.
To address the question of the impact of testosterone supplements on coronary artery disease, a team led by scientists at the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge turned to a technique known as Mendelian randomisation. Mendelian randomisation involves using genetic variants as a way of exploring causal links between exposures (often to environmental factors) and disease.
In this case, using data from more than 400,000 adults recruited to UK Biobank and over 1 million individuals recruited to CARDIoGRAMplusC4D, the researchers looked for genetic variants that lead to higher levels of testosterone in the blood and examined whether carriers of these variants were at a greater or lesser risk of coronary artery disease.
The results are published in the Journal of Clinical Endocrinology and Metabolism.
The team found that for men, having genetically higher testosterone was linked to a 17% higher risk of coronary artery disease. Previous studies have suggested that an individual's risk of coronary artery disease is 7.3% over their lifetime - testosterone supplementation would raise this to 8.5%. The increased risk seemed to be in part due to the fact that testosterone raises blood pressure.
The researchers argue that the reason this appears to contradict observational studies is most likely explained by other, confounding health factors such as diabetes and obesity. People with these conditions tend to have lower testosterone levels and greater risk of coronary artery disease.
The researchers found no clear link between testosterone and risk of coronary artery disease in women.
Emily Morbey, a PhD student at the MRC Epidemiology Unit and King's College, University of Cambridge, said: "More and more men are taking testosterone supplements, in part because of greater awareness of hypogonadism in men, but also because of increased marketing and social media trends, particularly targeted at younger men.
"Our work indicates that high levels of testosterone in the blood increase the risk of coronary artery disease, which in turn can put people at risk of heart attack and heart failure. When there is a medical need to boost testosterone, the benefits are likely to outweigh the risks, but this might not necessarily be the case when taken to boost performance."
Senior author Professor Ken Ong, also from the MRC Epidemiology Unit, said: "The US Food and Drug Administration has already issued guidance on the potential cardiovascular risk associated with testosterone supplementation. In the UK, there is no national guidance on the potential cardiovascular risk of high levels of testosterone. Our results suggest there's a need for more consistent warnings."
The research was funded by the Medical Research Council, with additional support from the National Institutes for Health and Care Research Cambridge Biomedical Research Centre.
Reference
Morbey, EJ et al. Higher circulating testosterone linked to higher CAD risk in men: Mendelian randomisation and survival analyses. JCEM; 24 Oct 2025; DOI: 10.1210/clinem/dgaf582
