It has long been believed that testosterone shortens men’s lives. Studies on neutered animals and Korean eunuchs seem to support this. However, a new study in the Annals of Internal Medicine questions these findings.
Researchers at the University of Western Australia led a study combining results from 11 high-quality studies (a meta-analysis) examining testosterone levels’ effect on lifespan.
The studies followed men for at least five years and found those with the lowest testosterone levels were more likely to die.
Death in this study was from any cause, but a deeper look into the analysis shows that this is mainly due to heart disease – still the leading cause of death in men worldwide.
Interestingly, the same process causing heart disease might also lead to erectile dysfunction — the inability to get and keep an erection firm enough for sex.
Erectile dysfunction often appears much earlier than heart disease symptoms and can be an early warning sign of current or future heart problems. Testosterone significantly affects erectile function, linking this hormone to heart disease.
Testosterone levels usually decline as men age, dropping by about 1% per year from the age of 30. This is sometimes called the male menopause or andropause.
This decrease is partly due to a slow decline in the testicles’ ability to produce testosterone and a reduction in the signals that tell them to. However, other factors can speed up this decline, including chronic disease.
So is low testosterone causing disease or is it caused by it?
A limitation of the new study is that it cannot determine if low testosterone directly causes an increased risk of death.
Testosterone is lowered by illness, so it could be a marker for an underlying disease that increases the chance of dying. This is especially true for diseases with long-term inflammation, like obesity.
Helping to untangle this relationship is the situation with prostate cancer patients. When the cancer spreads, the patient is given drugs that drastically lower testosterone levels. While this treatment improves prostate cancer, it increases the risk of heart attack and stroke in patients.
So while low testosterone may be a marker of disease, it is also a contributing factor in developing future disease and possibly death.
Figuring out what a “low” level of testosterone is can be complicated. Measuring testosterone alone might not give the full picture of what’s the right level for someone. What is low for one man may not be low for another.
Researchers use average testosterone levels from many people across different populations to establish normal ranges to help identify people outside of this range with a related disease. This helps doctors to identify and treat patients who might need help.
However, making these generalizations across populations is tricky and often requires larger effects to show these trends. The new meta-analysis suggests that the increased risk of death in men is mostly when testosterone levels are very low.
What is important to note from this is that regardless of the levels defining what is considered normal for any individual, lowered levels for that person seem to increase the risk of dying.
Given the risks of low testosterone, you might wonder if there is any way to prevent them.
First, men should avoid things that reduce it by adopting a healthy lifestyle and avoiding gaining weight. But when levels are low, treatment to replace the missing testosterone could be an option.
There is growing evidence that testosterone replacement therapy may help reduce some of those risks, including death from any cause and from heart attack, in some men. Yet controversy still exists as long-standing – and largely outdated – concerns regarding testosterone therapy causing heart attacks endure.
While most evidence now suggests there is at least no risk of heart disease associated with testosterone replacement therapy, more research is needed to determine if it can improve heart health in men.
While there may be hope on the horizon in the form of testosterone for reducing the risk of men dying from heart attack, it looks as though it will be a long road until treatment becomes a common option. In the meantime, it would be wise to maintain your testosterone levels through a healthy lifestyle.
Daniel Kelly, Senior Lecturer in Biochemistry, Sheffield Hallam University
