How Does Testosterone Affect Cancer Growth?
Testosterone can help some tumors grow. In others, it seems to slow them down. Which one happens depends on the type of cancer, where the tumor sits in the body, and how the hormone affects the immune system.
That’s why the effects of testosterone on cancer growth look so different from one disease to the next. Prostate cancer is the best-known case of a tumor that feeds on testosterone. New research suggests that brain cancer, and possibly colorectal cancer, may work the other way. If you or someone you love is weighing testosterone replacement therapy (TRT) during or after cancer, these differences matter.
How Does Testosterone Normally Affect Cancer Growth?
Testosterone isn’t considered a direct cause of cancer. But it can affect how some cancers grow once they’re there. In prostate, bladder, esophageal, head and neck, and stomach cancers, testosterone can act as a growth signal for tumor cells. Higher testosterone levels have also been linked to a higher risk, or faster progression, of liver cancer and melanoma.
Testosterone Can Increase Growth On Some Cancers
Prostate cancer depends on testosterone. Many prostate cancers have receptors that use testosterone as a signal to grow and divide. Doctors often use androgen deprivation therapy (ADT) to lower testosterone or block it from reaching cancer cells. This slows tumor growth and can cause cancer cells to die.
The effect changes with context. Testosterone can fuel cancer cells, suppress them, or do nothing at all. It depends on the organ, the tumor, and the patient’s biological sex.
Breast and endometrial cancer risk rises in women. Women with higher testosterone levels are at greater risk of developing these cancers.
Melanoma risk rises in men. Higher testosterone is linked to a greater risk of developing melanoma or having it progress in men. Male hormones can weaken the skin’s natural immune defenses against tumors.
Liver tumors use androgen signaling. In men, testosterone signaling helps liver tumors grow.
Bladder and lung tumors use it too. In these cancers, testosterone helps tumors survive, grow, and resist some treatments.
Blocking testosterone can boost immunity outside the brain. In many cancers outside the brain, lowering testosterone can improve the body’s immune response against tumors.
The Reverse Effect: Testosterone and Brain Cancer
Glioblastoma is an aggressive brain tumor. It’s more common in men than in women, and often more aggressive in men too. Yet research from Cleveland Clinic shows that testosterone and other androgens (male sex hormones) help slow glioblastoma growth in men. That’s the opposite of what testosterone does in most cancers outside the brain.
When researchers removed or blocked testosterone, they saw a chain reaction:
Stress hormones rose. Losing testosterone set off a stress-hormone response.
Immune cells shut down. Those stress hormones suppressed the immune cells that fight tumors.
Brain inflammation drove the process. Inflammation inside the brain kept the cycle going.
The tumor took advantage. With the immune system held back, the tumor had room to grow.
Key Findings
The brain plays by different rules. In prostate or lung cancer, testosterone often fuels tumor growth. In the brain, it acts more like a brake.
Low testosterone triggers a stress response. Removing testosterone causes inflammation in the hypothalamus, a control center deep in the brain. This floods the body with stress hormones and keeps immune cells from reaching the tumor, which lets it grow.
Survival data from real patients is encouraging. According to the NIH, men with glioblastoma who were already taking testosterone for unrelated reasons had a 38% lower risk of death. Their median survival was 16 months, compared with 12 months for men treated with chemotherapy alone.
Location shapes the response. Where a tumor grows often decides how hormones and the immune system interact. The blood-brain barrier creates a separate environment for testosterone signaling.
Testosterone keeps brain immunity balanced. In the nervous system, testosterone helps keep microglia (the brain’s immune cells) and local inflammation in check.
In brain cancer, testosterone seems to protect rather than fuel growth. A 2026 study in Nature found that healthy testosterone levels slowed glioblastoma progression in males. When levels dropped too low, the brain’s stress response went into overdrive and kept the immune system’s fighter cells away from the tumor.
Important: These findings are promising, but testosterone therapy is not an approved or standard treatment for brain cancer. Do not start testosterone without talking to your oncology team first.
Testosterone Also Acts in Colorectal Cancer
Early data suggest colorectal cancer may follow a similar reverse pattern. Normal or supplemental testosterone levels may offer some protection against advanced-stage colon cancer. Severe testosterone deficiency is generally linked to worse survival.
This evidence is still limited. It shows an association, not proof that testosterone protects against colorectal cancer. More research is needed before it can shape treatment decisions.
The Pros and Cons of Testosterone Replacement Therapy in Cancer Treatment
For people with cancer, TRT is a balancing act. It can relieve the symptoms of low testosterone, but it may also stimulate cancer cells that respond to hormones.
Pros (Potential Benefits)
Better quality of life for survivors with low testosterone. Men with hypogonadism (low testosterone) who have finished treatment and show no signs of active disease may get more energy, a better mood, and a stronger libido from TRT.
No strong evidence that it starts new cancers. Current evidence doesn’t show that testosterone causes new cancers. Its main risk is speeding up cancers that are already there.
Physical and metabolic gains. Bringing testosterone back to normal levels can improve bone density, lean muscle mass, insulin sensitivity, and overall body composition.
Growing evidence of safety under monitoring. Emerging research suggests TRT may be safe for some people with low-risk disease and no active tumors, as long as they’re closely monitored.
Cons (Risks and Drawbacks)
It can fuel existing tumors. In hormone-sensitive cancers, extra testosterone can speed the growth of existing or microscopic cancer cells.
It’s harmful in advanced disease. TRT should not be used in advanced prostate or breast cancer.
Heart and blood risks. TRT can increase red blood cell production. This raises the risk of blood clots, stroke, and heart attack, especially in people who already have heart disease.
Common side effects. These include fluid retention (edema), worse sleep apnea, acne, and lower sperm production.
The Wrap-Up
Testosterone affects each cancer differently. It can speed up hormone-sensitive cancers like prostate cancer. In brain cancer and possibly colorectal cancer, it may help slow the disease down. That’s why it’s important to understand how hormones interact with a specific cancer before making any treatment decision.
TRT can help people with low testosterone, but it also carries real risks. Researchers still need to learn more about when testosterone protects and when it harms. If you’re thinking about TRT, work closely with your oncology team so the decision fits your diagnosis, treatment history, and overall health.
