Men with low testosterone levels may face a higher risk of dying from cancer later in life, according to an international study involving more than 26,000 participants across Australia, Europe and the US.
The research, published in The Lancet Healthy Longevity, found that men with testosterone concentrations in the lowest fifth of the measured range had an 18 per cent higher risk of subsequent cancer death than those in the highest fifth.
Led by Professor Bu Yeap of the University of Western Australia's Medical School, the study analysed data from 11 long-running research projects. Researchers compared hormone measurements taken earlier in the participants' lives with cancer diagnoses and deaths recorded over subsequent years.
The team examined testosterone, dihydrotestosterone (DHT), sex hormone-binding globulin (SHBG) and luteinising hormone, which signals the testes to produce testosterone.
The findings suggest that low testosterone could be a marker of underlying health risks, although researchers stressed that the study does not establish that the hormone deficiency itself causes cancer.
At what testosterone level did cancer risk increase?
The researchers identified 8.6 nanomoles per litre (nmol/L) as the threshold below which subsequent cancer risk began to rise.
Professor Yeap said testosterone concentrations in healthy younger men typically range from 10 to 30 nmol/L, although levels generally decline with age.
Testosterone can also be influenced by factors including body mass index and physical activity, as well as medical conditions such as diabetes.
"We saw that when baseline testosterone was below 8.6 nmol/L, subsequent cancer risk started increasing," Yeap said.
He added that measuring testosterone could potentially help identify men who may face poorer health outcomes if they develop cancer in the future.
However, the researchers did not suggest that testosterone testing could predict an individual's cancer risk or replace established screening and diagnostic methods.
What did the study find about prostate cancer?
Despite longstanding questions about the relationship between testosterone and prostate cancer, the study found no association between naturally occurring testosterone concentrations and the risk of developing the disease.
This is an important distinction because reducing testosterone levels is an established treatment approach for prostate cancer.
Instead, researchers found that lower concentrations of SHBG and luteinising hormone were associated with a greater risk of prostate cancer.
The findings suggest that different hormones may have distinct relationships with cancer outcomes, rather than testosterone levels alone determining prostate cancer risk.
The researchers also cautioned against interpreting the results as a reason for men to take testosterone replacement therapy or supplements to prevent cancer.
"While we've shown low levels are associated with increased risk, we haven't got any evidence yet that actually giving men testosterone will reduce that risk," Yeap said.
He advised men found to have unexpectedly low testosterone to seek medical assessment, as further checks could identify other health conditions or risk factors.
"It could be a wake-up call and encouragement for men to engage in more healthy lifestyle behaviours, and to get regular, holistic checkups to stay on top of their health," he said.
The study adds to research into the relationship between hormone levels and long-term health, but further investigation is needed to establish why low testosterone is associated with higher cancer mortality and whether it has any direct role in disease development.
