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Does Testosterone Cause Prostate Cancer?

As men age, their testosterone levels can fall: by one estimate, 39% of men aged 45-85 have blood testosterone levels considered low (less than 300 ng/mL). Many have no symptoms, but some men may experience symptoms such as low mood, low energy, weight gain, and low sex drive, leading them to seek evaluation and treatment. In consultation with their doctor, they may consider testosterone supplements. Testosterone supplementation is becoming more common: between 2000 and 2011, the number of prescriptions of testosterone filled by U.S. pharmacies increased tenfold.

What does this have to do with prostate cancer? Prostate cancer is related to male hormones, and medications that block testosterone are used to treat certain types of prostate cancer. Men taking testosterone supplements might worry whether they are putting themselves at risk for prostate cancer in the future. Patients who have been diagnosed with prostate cancer and who previously took supplements may wonder: did the testosterone cause my cancer?

Fuel for existing prostate cancer

In his 2018 book The Virility Paradox (BenBella Books), PCF’s President and CEO, Dr. Chuck Ryan, wrote extensively on the complicated role of testosterone in the human body. He notes that testosterone does not cause prostate cancer, but it can fuel prostate cancer that already exists. Biologically, there is a difference between initiating cancer vs. promoting cancer once it has already started. Testosterone does the latter for prostate cancer.

If a man taking testosterone is diagnosed with prostate cancer, it’s not a cause-and-effect relationship. However, men taking testosterone should be monitored by a physician, including checking their PSA. This may lead to a greater likelihood of being diagnosed with prostate cancer – simply because a doctor is looking for it.

Testosterone after prostate cancer

Men can live for decades following therapy for localized prostate cancer, and may develop symptoms of low testosterone as they age. Men who have taken hormone therapy (androgen deprivation therapy) may have trouble recovering to normal testosterone levels. Are supplements a treatment option? Several studies suggest that testosterone therapy may be safe in select patients with a history of prostate cancer, but there is not enough evidence to definitively quantify the risks vs. the benefits. Long-term, randomized clinical trials are needed.

For treatment of advanced prostate cancer, researchers are investigating the role of high-dose testosterone supplementation. Known as bipolar androgen therapy, testosterone is given at scheduled intervals while patients are also taking hormone-blocking therapy. This causes alternating (“bipolar”) very high and very low testosterone levels. Unable to adapt to the rapidly-changing environment, the cancer cells die.

Talk to your doctor

If you are considering testosterone supplements to treat symptoms of low testosterone, talk to you doctor to gain a thorough understanding of the benefits and risks. If you’ve had prostate cancer, be sure to tell your doctor, and note any history of prostate or other cancer in your family. Ask about getting a baseline PSA level before you start the medication, and follow your doctor’s recommendations about monitoring your testosterone and PSA levels while you’re taking the supplements, and beyond.

Becky Campbell
Becky Campbell develops medical content at the Prostate Cancer Foundation. She has previously worked in outcomes research and in science education.