Testosterone and Prostate Cancer: Low T and the Harm It Can Cause

For decades, men have been warned that testosterone is dangerous! Federal regulatory organizations have warned physicians that this hormone might fuel prostate cancer, trigger heart attacks, or shorten life. That belief has shaped medical practice, prescribing habits, and fear around testosterone therapy. But the science is shifting. Is there really a causative link between testosterone and prostate cancer? Are there any negative consequences associated with long-term testosterone suppression? Let’s catch up on this controversial topic thanks to a question from a reader.

Testosterone and Prostate Cancer: Why Lower Isn’t Always Better

A few weeks ago we heard from a visitor to this website. He was responding to an article we wrote about testosterone and heart disease:

Testosterone Heart Risk: Was the FDA Warning Wrong for a Decade?
A reader’s concern about testosterone heart risk prompts a look at new evidence, FDA changes—and why untreated low T can be dangerous, too.

Q. You recently wrote that testosterone does not increase the risks for heart attacks. But you overlooked the real risk of testosterone therapy: cancer!

I survived advanced prostate cancer seven years ago by having my testes removed because prostate cancer needs testosterone to grow. Most men with prostate cancer get leuprolide injections for several months to suppress testosterone production while they wait for radiation or surgery. They get off it as quickly as possible though, because men would rather die than give up sex.

A. We understand your concerns. The message has been for years that testosterone is dangerous. This hormone might fuel prostate cancer, trigger heart attacks, or shorten life. That belief has shaped medical practice, prescribing habits, and fear around testosterone therapy.

Many physicians believed that the more testosterone a man had circulating in his system, the greater the risk for prostate cancer. The FDA was adamant that extra testosterone was a problem for cardiovascular disease.

But scientific inquiry and further study often shifts dominant paradigms.

A large clinical trial published in the New England Journal of Medicine (July 13, 2023) contradicted old beliefs. It concluded that testosterone replacement therapy (TRT) did not contribute to cardiovascular events. Read the details here. The same study also determined that men with low PSA levels were no more likely to develop prostate cancer on TRT than on placebo (JAMA Network Open, Dec. 27, 2023).

As you note, prostate cancer is frequently treated with androgen deprivation therapy (ADT).

Testosterone and Prostate Cancer: A Fundamental Concept!

The idea that testosterone “feeds” prostate cancer has been deeply ingrained in medicine. And it is absolutely true that advanced prostate cancer is almost always treated by first lowering testosterone levels, either with medications such as leuprolide or surgically by removing the testes.

What about men who do not have prostate cancer? Many healthcare professionals believe that men who get testosterone therapy could develop prostate cancer even if they don’t have it now.

What Did Earlier Research Report About Testosterone and Prostate Cancer?

A large Swedish analysis of more than 250,000 medical records, presented at the American Urological Association meeting in May 2016, found that men prescribed testosterone for over a year were not more likely to be diagnosed with prostate cancer.

In fact, those men appeared to have a lower risk of aggressive prostate cancer.

That research challenged the fear that testosterone therapy inevitably leads to malignancy and suggested that withholding testosterone from men who truly need it may do more harm than good.

The Flip Side of the Story: When Men Develop Low T

Strap in, because this side of the story rarely gets told.

Lowering testosterone can be lifesaving in prostate cancer — but it is not benign.

A large study published in JAMA Network Open (July 3, 2019) followed nearly 155,000 older men with prostate cancer for over a decade. Those who received androgen deprivation therapy had significantly higher rates of dementia and Alzheimer’s disease than those who did not.

• 21.6% of men receiving ADT developed dementia
• 15.8% of men not receiving ADT did

The researchers calculated a number needed to harm of:

• 18 for Alzheimer’s disease
• 10 for dementia

That means for every 10 men exposed to prolonged testosterone suppression, one additional case of dementia could be expected over time.

These findings are bolstered by a more recent study of Swedish men (European Urology Oncology, Aug. 2025). In this analysis, 178,746 men with prostate cancer were matched to 1,787,460 men with no prostate cancer. None of the men had dementia at the start of the study. Those whose prostate cancer was treated exclusively with ADT had a higher risk of both Alzheimer disease and vascular dementia. Other prostate cancer treatments did not increase the risk for dementia.

Testosterone and Prostate Cancer Therapy: A Brutal Tradeoff

Testosterone is not a disposable hormone.

When levels fall too low, men face increased risks of:

• Muscle wasting and weakness
• Bone loss and osteoporosis
• Depression and cognitive difficulties
• Erectile dysfunction and loss of libido
• Hot flashes and metabolic changes

Of course men with high-grade prostate cancer may need to accept such complications to avoid metastatic disease and bad consequences of this malignancy.

Testosterone and Prostate Cancer: Making Sense of Confusing Data

Here is what seems increasingly clear:

• Testosterone therapy does not appear to cause prostate cancer in men without the disease.
• Suppressing testosterone can slow prostate cancer progression, but it carries risks.
• Low testosterone is not harmless, especially over months or years.
• Men deserve honest conversations about both benefits and harms.

Medicine does not offer perfect answers here — only tradeoffs.

Men considering testosterone therapy, and men undergoing prostate cancer treatment, should be given clear information, not outdated fear. Decisions should be individualized, revisited often, and guided by evolving evidence, not medical dogma.