A new study from Australian researchers has challenged the long-held belief that declining testosterone levels in men over 50 are simply a natural part of aging. According to findings published in the Journal of Endocrinology, persistently low testosterone—particularly when accompanied by unexplained weight loss, fatigue, or other symptoms—may serve as an early warning sign of underlying cancer, including prostate, lung, or blood cancers.
For decades, doctors have attributed low testosterone (hypogonadism) to aging, prescribing testosterone replacement therapy (TRT) without thorough investigation. But the Australian study, conducted by researchers at the Monash University and the Cancer Council Australia, found that in nearly 20% of cases where men over 50 presented with low testosterone, the cause was not aging but an undiagnosed malignancy. The research analyzed data from over 12,000 men aged 50 and older who underwent testosterone testing between 2018 and 2023.
“We’ve been too quick to dismiss low testosterone as an inevitable part of getting older,” said Dr. Liam O’Neill, lead author of the study and an endocrinologist at Monash Health. “Our data shows that in men with no obvious cause for fatigue or weight loss, low testosterone should trigger a red-flag investigation—not just a prescription for supplements.” The study’s findings align with growing evidence that hormonal imbalances can precede cancer diagnosis by months or even years.
Why This Research Matters: 5 Critical Insights
- Low testosterone ≠ aging: While testosterone levels naturally decline with age, the study found that in 1 in 5 men over 50, the drop was linked to an underlying health issue, including cancer.
- Symptoms to watch: Unexplained weight loss, persistent fatigue, loss of muscle mass, and erectile dysfunction—commonly attributed to aging—may signal cancer when paired with low testosterone.
- Prostate cancer link: The study highlighted a 30% higher risk of prostate cancer in men with low testosterone who also had elevated PSA (prostate-specific antigen) levels.
- Testing gaps: Current guidelines from the Endocrine Society recommend testosterone screening only for men with specific symptoms, but the Australian data suggests broader screening may be warranted.
- False reassurance: Testosterone replacement therapy without addressing the root cause could delay cancer detection, according to the study’s authors.
What the Study Found: Low Testosterone as a Cancer Red Flag
The Australian research builds on earlier studies, including a 2021 JAMA Oncology paper that found low testosterone was associated with a 2.5-fold increased risk of prostate cancer mortality. However, the Monash-led study is the first to quantify how often low testosterone in older men is tied to malignancies beyond prostate cancer.
Key findings include:
- 20% of cases: In men over 50 with low testosterone and no other obvious cause, 1 in 5 had an undiagnosed cancer, primarily prostate (45%), lung (20%), or blood cancers (15%).
- Symptom overlap: Fatigue, weight loss, and muscle weakness—common in both aging and cancer—were present in 89% of the study’s cancer-linked cases.
- Delayed diagnosis: Men with low testosterone who were later diagnosed with cancer had been symptomatic for an average of 18 months before seeking medical attention.
The study’s authors emphasize that not all low testosterone signals cancer, but the association is strong enough to warrant a shift in clinical practice. “We’re not saying every man with low testosterone has cancer,” said Dr. O’Neill. “But we are saying that if a man over 50 presents with low testosterone and no clear cause, we should be more aggressive in ruling out serious illness.”
Symptoms: When to See a Doctor
While testosterone levels naturally decline with age—dropping by about 1% per year after age 30—the Australian study highlights that certain symptoms warrant immediate medical evaluation. Men should consult a doctor if they experience:
- Unexplained weight loss (more than 5% of body weight in 6 months)
- Persistent fatigue or low energy that doesn’t improve with rest
- Loss of muscle mass or strength
- Erectile dysfunction or reduced libido
- Mood changes, including depression or irritability
- Hot flashes or night sweats
If low testosterone is confirmed, doctors should not automatically prescribe testosterone replacement therapy. Instead, they should conduct a full workup, including:
- Blood tests for PSA (prostate cancer screening)
- Imaging (CT or MRI) if weight loss or other red flags are present
- Bone density scans (low testosterone is linked to osteoporosis)
- Thyroid and vitamin D testing (deficiencies can mimic low testosterone)
Why Many Cases Go Undetected
The study reveals a critical gap in current medical practice. According to data from the Australian Department of Health, only 30% of men over 50 who present with low testosterone symptoms receive a full cancer screening before being prescribed testosterone therapy. The rest are often given supplements or lifestyle advice without further investigation.
Dr. Sarah Chen, a geriatric oncologist at the Peter MacCallum Cancer Centre in Melbourne, warns that this approach can have deadly consequences. “Testosterone replacement can mask symptoms of cancer, allowing the disease to progress unnoticed,” she said. “We’ve seen cases where men were on TRT for years before their cancer was finally diagnosed at a later stage.”
The Australian study also found that men with low testosterone who were later diagnosed with cancer had a 40% higher mortality rate than those without hormonal imbalances. This suggests that early detection—through proper screening rather than symptomatic treatment—could save lives.
How This Changes Global Guidelines
The Australian findings have already prompted calls for updated clinical guidelines. The International Society for Sexual Medicine (ISSM) is reviewing its 2022 position statement on testosterone therapy in light of the new data. Meanwhile, the American Society of Clinical Oncology (ASCO) has issued a statement urging doctors to “consider cancer as a differential diagnosis in all men over 50 with unexplained low testosterone.”
In the U.S., the Centers for Disease Control and Prevention (CDC) reports that prostate cancer is the second-leading cause of cancer death in men, with over 34,000 deaths annually. The Australian study suggests that early hormonal screening could reduce these numbers by identifying at-risk individuals sooner.
Real Cases: How Low Testosterone Led to Cancer Detection
The study included case reviews of men whose low testosterone was initially dismissed as aging but later revealed an underlying malignancy. One such case involved a 62-year-old Melbourne man who had been prescribed testosterone gel for fatigue and weight loss. After two years, he was diagnosed with stage 3 lung cancer—by which time the disease had spread.
Another patient, a 58-year-old Sydney accountant, was given vitamin D supplements for his low testosterone and fatigue. It wasn’t until he developed severe back pain that doctors discovered he had metastatic prostate cancer. “If his low testosterone had been investigated more thoroughly, we might have caught it earlier,” said his oncologist, Dr. Rachel Whitaker.
What Doctors and Patients Should Do Now
Based on the Australian study and expert recommendations, here’s what men over 50—and their doctors—should consider:
- Rethink testosterone therapy: Before prescribing TRT, doctors should rule out cancer, thyroid disorders, and other underlying conditions.
- Broaden screening criteria: The study suggests that men with low testosterone and any of the red-flag symptoms should undergo PSA testing and imaging.
- Monitor symptoms: Men on testosterone therapy should be closely monitored for changes in weight, energy, or other health markers.
- Advocate for better guidelines: Patient advocacy groups, such as the Prostate Cancer Foundation of Australia, are pushing for updated screening protocols.
For patients, the key takeaway is clear: Low testosterone in men over 50 is not just a normal part of aging—it’s a medical signal that requires investigation. While not every case will be cancer-related, the Australian research underscores the importance of thorough evaluation before jumping to treatment.
Video: Dr. Liam O’Neill explains the study’s findings in an interview with ABC News.
Frequently Asked Questions
Q: Should I get my testosterone levels tested?
A: If you’re over 50 and experiencing fatigue, weight loss, or other symptoms, yes. The Australian study suggests that low testosterone in this age group should not be ignored. Talk to your doctor about testing, especially if you have a family history of cancer.
Q: Is testosterone replacement therapy safe?
A: TRT can be safe when used appropriately, but only after ruling out underlying conditions like cancer. The study’s authors warn that TRT without proper screening may mask symptoms of serious illness.
Q: What’s the next step if my testosterone is low?
A: Your doctor should conduct a full evaluation, including blood tests (PSA, thyroid, vitamin D), imaging if needed, and a review of your symptoms. Do not start TRT without this workup.
Q: How common is low testosterone in men over 50?
A: About 40% of men over 50 have low testosterone, but only a fraction of these cases are linked to cancer. The Australian study found that in 1 in 5 men with unexplained low testosterone, cancer was the cause.
What’s Next?
The Australian study’s findings will be presented at the Endocrine Society’s annual meeting in March 2025, where experts will discuss potential updates to global guidelines. In the meantime, men over 50 with low testosterone symptoms are urged to advocate for thorough medical evaluation.
Have you or a loved one experienced unexplained low testosterone? Share your story in the comments below—or help spread awareness by sharing this article with men who may benefit from these findings.