Study Links Very Low Testosterone Levels to Greater Risk of Cancer Death

Men with very low testosterone levels may face a significantly higher risk of dying from cancer, according to a large international analysis of long-term health data. The study, published in The Lancet Healthy Longevity, pooled data from 11 cohort studies and was conducted by an international team of researchers examining the relationship between testosterone levels and long-term cancer outcomes. The findings suggest that very low testosterone could serve as an important marker of overall health and future cancer risk rather than being a direct cause of cancer itself.

The researchers analyzed data from more than 26,000 men who were followed for at least five years. Participants ranged from younger adults to older men, allowing scientists to examine hormone levels across a broad age range and investigate how they related to later cancer diagnoses and deaths.

How the Study Was Conducted

Researchers measured blood testosterone concentrations in nanomoles per liter (nmol/L), the standard clinical unit used worldwide. In healthy young men, testosterone levels typically range between approximately 10 and 30 nmol/L, although concentrations naturally decline with age and may also decrease because of chronic illness.

The researchers then compared cancer incidence and cancer-related deaths among men in the lowest fifth of testosterone levels with those in the highest fifth. Even after adjusting for age, smoking status, body weight, and other health-related factors, very low testosterone remained associated with poorer cancer outcomes.

Key Testosterone Thresholds

The analysis found that cancer mortality increased once testosterone levels dropped below 8.6 nmol/L. Men within this very low range were significantly more likely to die from cancer during follow-up than men with higher testosterone concentrations.

The likelihood of being diagnosed with cancer also increased when testosterone levels fell below 7.3 nmol/L. These findings suggest that extremely low testosterone may serve as a warning sign for both an increased likelihood of developing cancer and a poorer prognosis after diagnosis.

Prostate Cancer Was Different

Despite the overall association between low testosterone and cancer risk, the researchers found no evidence that natural testosterone levels influenced the likelihood of developing or dying from prostate cancer.

This finding is particularly noteworthy because prostate tissue is highly responsive to testosterone. Advanced prostate cancer is commonly treated by dramatically lowering testosterone levels, leading to longstanding questions about whether naturally high testosterone might increase prostate cancer risk. This large analysis, however, found no such relationship.

Instead, lower levels of two related hormones—sex hormone-binding globulin (SHBG) and luteinizing hormone (LH)—were associated with a greater likelihood of prostate cancer diagnosis. The researchers note that these hormonal interactions remain complex and require further investigation.

Low Testosterone Is Likely a Marker, Not a Cause

The authors emphasize that the study does not demonstrate that low testosterone directly causes cancer.

Rather, very low testosterone may reflect underlying health problems that also increase cancer risk or worsen cancer outcomes. Conditions such as chronic inflammation, obesity, diabetes, cardiovascular disease, and frailty are all known to suppress testosterone production while independently increasing cancer risk.

Because this was an observational study, it cannot determine whether increasing testosterone levels would reduce cancer risk. The researchers specifically caution against using testosterone replacement therapy solely to prevent cancer.

What Men Should Do

Experts advise that men with very low testosterone should view the finding as a reason for a comprehensive medical assessment rather than a cause for panic.

Doctors typically confirm low testosterone with repeat blood tests while also evaluating symptoms such as reduced libido, fatigue, loss of muscle mass, erectile dysfunction, or low mood. Testosterone replacement therapy is generally considered only for men who have both consistently low hormone levels and clinically significant symptoms.

For many individuals, improving overall health remains the most important intervention. Maintaining a healthy weight, exercising regularly, avoiding smoking, limiting alcohol intake, getting sufficient sleep, and managing chronic medical conditions can all help support healthy testosterone levels while reducing overall cancer risk.

Implications for Future Research

The findings add to growing evidence that hormone health may play an important role in predicting long-term cancer outcomes.

Researchers suggest that testosterone measurements could eventually become one component of personalized cancer risk assessment alongside established factors such as age, smoking history, obesity, family history, and metabolic health.

Future studies will investigate whether changes in testosterone over time provide better prediction than a single blood measurement. Scientists also hope to determine whether men with persistently low testosterone respond differently to specific cancer treatments.

For now, the researchers conclude that very low testosterone should be viewed less as a direct cause of cancer and more as an important warning sign that a man's overall health—and potentially his long-term cancer risk—deserves closer medical attention.