TRT and Prostate Health: Does Testosterone Cause Prostate Cancer?

The Fear That Keeps Men From Getting Treatment

You have been dealing with the symptoms for a while now. The fatigue that will not let up. The vanishing sex drive. The muscle loss despite consistent training. You got your labs done. Your testosterone came back low. Your doctor mentioned TRT as an option. And then — either from the internet, a well-meaning friend, or an outdated physician — you heard the thing that stopped you in your tracks:

"Testosterone causes prostate cancer."

That single sentence has kept more men from treating clinically low testosterone than any other claim in men's health. It is repeated in waiting rooms, on forums, and even by some physicians who have not updated their understanding of the research. And for decades, it was considered medical gospel.

But it is wrong. Or at the very least, it is a dramatic oversimplification that modern evidence no longer supports.

The relationship between testosterone and prostate cancer is one of the most studied — and most misunderstood — topics in urology and endocrinology. Over the past 15 years, landmark clinical trials, large meta-analyses, and a fundamental rethinking of the underlying biology have systematically dismantled the old paradigm. Today, the consensus among leading researchers is clear: testosterone replacement therapy, when properly prescribed and monitored, does not increase the risk of developing prostate cancer.

This article lays out exactly what the evidence says, where the myth came from, what you should actually be monitoring, and how to make an informed decision without letting decades-old fear dictate your health.

Where the Myth Started: Huggins, Castration, and a Nobel Prize

The belief that testosterone drives prostate cancer traces back to a single study published in 1941 by Dr. Charles Huggins and Clarence Hodges. They demonstrated that castrating men with advanced, metastatic prostate cancer caused their tumors to regress. When they administered testosterone to these castrated men, the cancer markers rose again.

This finding was groundbreaking for cancer treatment. Huggins won the Nobel Prize in 1966 for establishing androgen deprivation therapy — the practice of surgically or chemically lowering testosterone to near-zero levels to slow advanced prostate cancer. Androgen deprivation remains a standard treatment for metastatic prostate cancer to this day.

But here is where the logic went wrong. From the observation that removing testosterone slows existing advanced cancer, the medical community extrapolated that adding testosterone must cause cancer. This is the equivalent of noticing that removing oxygen slows a house fire and concluding that oxygen caused the fire. Oxygen is necessary for fire to burn, but it does not ignite it.

For more than 60 years, that extrapolation was accepted without challenge. Physicians were taught in medical school that testosterone feeds prostate cancer, and prescribing testosterone to any man was considered inherently dangerous. The result: millions of men with clinically low testosterone were denied treatment — or never even evaluated — because of a fear rooted in a case series of three patients from 1941.

The Saturation Model: Why More Testosterone Does Not Mean More Cancer Risk

The modern understanding of testosterone and prostate tissue is built on the saturation model, first proposed by Dr. Abraham Morgentaler at Harvard Medical School and subsequently validated by multiple research groups.

The saturation model works like this: prostate cells have a finite number of androgen receptors. Once those receptors are fully occupied — which occurs at relatively modest testosterone levels (approximately 230 to 250 ng/dL of serum testosterone) — additional testosterone has no further growth-stimulating effect on prostate tissue. The receptors are saturated. Adding more testosterone beyond the saturation point is like pouring water into a glass that is already full.

This explains several observations that the old model could not:

• Men with naturally high testosterone do not have higher prostate cancer rates than men with low or average testosterone
• Raising testosterone from low to normal through TRT does not produce the prostate growth you would expect if the "more testosterone equals more risk" model were correct
• Castration works for advanced cancer because it drops testosterone below the saturation point — essentially depriving receptor-saturated cancer cells of the minimum androgen they need to function
• Prostate cancer cells in normal-range men are already bathed in more than enough testosterone. Adding a therapeutic amount changes nothing at the receptor level.

The Mayo Clinic's current position, updated in 2025, states it plainly: "Testosterone itself is not likely to increase a person's risk of developing prostate cancer." They note that while testosterone can help existing cancer cells grow, the saturation model means that levels above the saturation threshold provide no additional growth stimulus.

The TRAVERSE Trial: The Evidence That Changed Everything

If the saturation model provided the theory, the TRAVERSE trial provided the proof at scale.

Published in JAMA Network Open in 2024, the TRAVERSE trial is the largest randomized, placebo-controlled study ever conducted on TRT safety. It enrolled 5,204 men aged 45 to 80 with documented hypogonadism (low testosterone) and followed them for an average of 33 months — a total of 14,304 person-years of data.

The prostate safety results were unequivocal:

Prostate Event	TRT Group (n=2,596)	Placebo Group (n=2,602)	Significant Difference?
High-grade prostate cancer	5 cases (0.19%)	3 cases (0.12%)	No (P = 0.51)
Any prostate cancer	Low incidence	Low incidence	No
Acute urinary retention	Low incidence	Low incidence	No
Invasive prostate procedures	Low incidence	Low incidence	No
New prostate medication	Low incidence	Low incidence	No

The researchers concluded: "In a population of middle-aged and older men with hypogonadism, carefully evaluated to exclude those at high risk of prostate cancer, the incidences of high-grade or any prostate cancer and other prostate events were low and did not differ significantly between testosterone- and placebo-treated men."

This was not a small observational study. It was a rigorously designed randomized controlled trial — the gold standard of medical evidence. And the message was clear: TRT does not increase prostate cancer risk in men without pre-existing high-risk disease.

What the Broader Research Actually Shows

The TRAVERSE trial did not emerge in isolation. It confirmed findings from years of accumulating evidence:

Epidemiological Evidence

Multiple large population studies have examined men with different testosterone levels over long periods. The consistent finding is that men with higher natural testosterone levels do not develop prostate cancer at higher rates than men with low testosterone. Some studies have actually found a slightly inverse relationship — that lower testosterone is associated with more aggressive prostate cancer at diagnosis.

A 2016 meta-analysis published in Asian Journal of Andrology pooled data from prospective studies and found no significant association between baseline testosterone levels and prostate cancer risk. When studies did find associations, they were with low testosterone, not high.

TRT-Specific Studies

Numerous studies of men receiving TRT — both short-term and long-term — have consistently failed to show an increased prostate cancer incidence:

• A 2005 meta-analysis of 19 placebo-controlled TRT trials found no increased prostate cancer risk
• Long-term registry data from the European Male Ageing Study showed no increased risk with higher testosterone
• The Testosterone Trials (TTrials), a coordinated set of seven randomized trials, found no increased prostate events
• A 2023 systematic review in Reviews in Urology concluded that "the current body of evidence does not support the notion that TRT increases the risk of prostate cancer"

The Low Testosterone Paradox

Perhaps the most striking finding is what happens at the other end of the spectrum. Research has shown that men diagnosed with prostate cancer who also have low testosterone tend to have more aggressive disease — higher Gleason scores, more advanced staging, and worse outcomes. This is counterintuitive if you believe testosterone drives cancer, but it is consistent with the saturation model and with what we know about how hypogonadism affects cellular biology.

Low testosterone is associated with metabolic syndrome, obesity, insulin resistance, and chronic inflammation — all of which are independent risk factors for aggressive cancer. When you treat low testosterone and its metabolic consequences, you may actually be reducing the inflammatory and metabolic environment that aggressive cancers thrive in.

PSA and TRT: What That Rising Number Actually Means

One of the main sources of confusion — and anxiety — around TRT and prostate health is PSA (prostate-specific antigen). Many men starting TRT see their PSA increase in the first 3 to 6 months, and their immediate assumption is that something is wrong.

Here is what is actually happening.

PSA is a protein produced by prostate cells. Its production is partially regulated by testosterone. When you raise testosterone levels from low to normal via TRT, prostate cells become more metabolically active and produce more PSA. This is a normal physiological response — not evidence of cancer.

Think of it this way: if you had been dehydrated for years and then started drinking adequate water, your kidneys would produce more urine. That does not mean your kidneys are diseased. It means they are functioning normally under normal conditions.

What Is a Normal PSA Increase on TRT?

Studies consistently show that men starting TRT typically experience a PSA increase of 0.3 to 0.5 ng/mL in the first 6 to 12 months, which then stabilizes. This increase brings PSA to the level expected for a man with normal testosterone — it is essentially correcting an artificially low baseline.

PSA Scenario	What It Means	Action
PSA rises 0.3–0.5 ng/mL in first 6 months	Normal physiological response to testosterone normalization	Continue monitoring per schedule
PSA rises >1.4 ng/mL in first 12 months	Exceeds expected increase; warrants further evaluation	Repeat PSA, consider urology referral
PSA velocity >0.75 ng/mL per year sustained	Elevated rate of change regardless of absolute value	Urology referral recommended
Absolute PSA >4.0 ng/mL	Above standard threshold; requires workup	Urology referral, possible biopsy
PSA stable after initial rise	Prostate has reached new equilibrium at normal testosterone	Continue routine monitoring

BPH and Testosterone: Does TRT Make Your Prostate Grow?

Beyond cancer, many men worry about benign prostatic hyperplasia (BPH) — the age-related prostate enlargement that causes urinary symptoms like frequent urination, weak stream, nighttime bathroom trips, and difficulty emptying the bladder.

The intuitive assumption is that adding testosterone would enlarge the prostate further. The research tells a more nuanced story.

A 2021 study published in Investigative and Clinical Urology examined the relationship between testosterone levels and prostate volume over four years. The findings were the opposite of what most people would expect: men with low testosterone had significantly larger prostate volumes than men with normal testosterone (26.86 mL vs. 24.06 mL). After adjusting for age, higher testosterone levels were actually associated with smaller prostate volume.

This counterintuitive finding has several explanations:

• Metabolic factors: Low testosterone is associated with obesity, insulin resistance, and higher cortisol — all of which promote prostate growth through inflammatory and metabolic pathways independent of androgens
• Estrogen conversion: Men with low testosterone and higher body fat have more aromatase activity, converting testosterone to estradiol. Estrogen is actually a stronger driver of prostate cell proliferation than testosterone in BPH
• DHT saturation: Similar to the cancer saturation model, intraprostatic DHT levels remain relatively stable across a wide range of serum testosterone — the prostate tightly regulates its own androgen exposure

Clinical TRT studies confirm this. The TRAVERSE trial and others have shown no significant increase in urinary obstruction, acute urinary retention, or need for prostate surgery in men receiving TRT compared to placebo.

If You Already Have BPH

For men already diagnosed with BPH who are considering TRT, the evidence is reassuring. Multiple studies have shown that TRT does not significantly worsen lower urinary tract symptoms (LUTS) in men with pre-existing mild to moderate BPH. Some studies have even reported improvement in urinary symptoms on TRT — possibly through improved bladder muscle function and reduced metabolic inflammation.

That said, if you have severe BPH or urinary obstruction, close monitoring is still appropriate. Any new urinary symptoms on TRT should be evaluated promptly.

TRT After Prostate Cancer: The Emerging Evidence

Perhaps the most dramatic shift in thinking is around TRT for men who have already had prostate cancer and been successfully treated. For decades, this was considered an absolute contraindication — the one scenario where even TRT-friendly physicians drew the line.

That line is moving.

A growing body of evidence — including prospective studies and case series — has examined TRT in men after radical prostatectomy or radiation therapy for localized prostate cancer. The results have been surprisingly consistent:

• Multiple studies of men receiving TRT after radical prostatectomy for localized disease have shown no increase in biochemical recurrence (rising PSA suggesting cancer return)
• Studies of TRT after radiation therapy have similarly shown no increased recurrence
• Quality of life — including sexual function, energy, and body composition — improved significantly in these men

The American Urological Association now states that TRT can be considered in select men after prostate cancer treatment, depending on disease characteristics and shared decision-making with their urologist. This is a sea change from the blanket prohibition of 15 years ago.

Prostate Monitoring on TRT: What a Responsible Protocol Looks Like

The evidence is clear that TRT does not cause prostate cancer. But that does not mean you ignore the prostate once you start treatment. Responsible TRT prescribing includes prostate monitoring — not because TRT creates risk, but because prostate cancer is common in the age group that receives TRT, and catching it early matters regardless of testosterone status.

Here is what a proper monitoring protocol looks like:

Before Starting TRT

• Baseline PSA: Mandatory. This establishes your reference point for tracking changes
• Digital rectal exam (DRE): Recommended by most guidelines, especially for men over 50 or those with family history
• Review of risk factors: Family history of prostate cancer (especially first-degree relatives), African American heritage (higher baseline risk), prior abnormal biopsies
• Comprehensive blood work: Including total and free testosterone, hematocrit, metabolic panel, and estradiol

Ongoing Monitoring Schedule

Timepoint	Tests	What to Watch For
3 months after starting TRT	PSA, hematocrit, testosterone levels	Initial PSA response, hematocrit rise
6 months	PSA, full blood panel	PSA stabilization, dose optimization
12 months	PSA, comprehensive panel, DRE	Annual baseline established
Annually thereafter	PSA, blood panel, DRE	PSA velocity, hematocrit trends

Red Flags That Warrant Urology Referral

• PSA rise greater than 1.4 ng/mL within 12 months of starting TRT
• PSA velocity exceeding 0.75 ng/mL per year on sustained measurement
• Absolute PSA above 4.0 ng/mL (or above 3.0 ng/mL for younger men)
• Palpable nodule or asymmetry on DRE
• New onset of significant urinary symptoms (obstruction, hematuria)

At Heyday, prostate monitoring is built into the ongoing care protocol. Regular blood work includes PSA as a standard marker, and your provider tracks your PSA trajectory over time — not just isolated readings.

The Real Risk Factors for Prostate Cancer

If testosterone does not cause prostate cancer, what does? The honest answer is that prostate cancer — like most cancers — is multifactorial, and no single cause has been identified. But several risk factors are well established:

Risk Factor	Impact	Modifiable?
Age (over 50)	Primary risk factor — incidence rises sharply with age	No
Family history	2–3x higher risk with first-degree relative diagnosed	No
African American heritage	1.7x higher incidence and more aggressive disease	No
Obesity	Associated with higher-grade, more aggressive prostate cancer	Yes
Chronic inflammation	Inflammatory environment promotes carcinogenesis	Yes (partially)
Sedentary lifestyle	Associated with higher prostate cancer risk	Yes
Diet (high processed meat, low vegetables)	Modest association with increased risk	Yes
Metabolic syndrome	Insulin resistance and inflammation promote aggressive disease	Yes

Notice what is not on the list: testosterone replacement therapy. Also notice what is on the list: obesity, metabolic syndrome, sedentary lifestyle, chronic inflammation. These are the same conditions that low testosterone contributes to. There is a real argument that leaving low testosterone untreated may indirectly increase prostate cancer risk through worsening metabolic health — though this remains an area of active research.

The Bottom Line

The fear that testosterone replacement therapy causes prostate cancer is based on an extrapolation from a 1941 case series that has been systematically dismantled by modern research. The saturation model explains why testosterone levels above the saturation threshold have no additional effect on prostate cell growth. The TRAVERSE trial — the largest and most rigorous RCT of TRT safety ever conducted — showed no increased risk of prostate cancer or other prostate events. Population studies consistently fail to find a link between higher testosterone and prostate cancer. And even the once-absolute prohibition against TRT after prostate cancer treatment is being reconsidered.

None of this means you should ignore prostate health. Prostate cancer is the second most common cancer in men, and age is the biggest risk factor. Regular screening with PSA and clinical exams is important for all men over 50, regardless of testosterone status. But the decision to screen and monitor is separate from the decision to treat low testosterone.

If you have clinically low testosterone with symptoms — the crushing fatigue, the absent libido, the brain fog, the disappearing muscle, the mood swings — prostate cancer fear should not be the reason you suffer in silence. The evidence does not support it. What the evidence does support is proper screening before starting TRT, regular monitoring during treatment, and working with a provider who stays current with the research.