Men who undergo testosterone replacement therapy due to a drop in testosterone levels might not be at an increased risk of getting prostate cancer as previously thought, a new study from the U.K. suggests.


Researchers looked at nearly 1,400 men receiving testosterone replacement therapy for up to 20 years, and found that 14 cases of prostate cancer developed over the study period.


That number equates to one prostate cancer diagnosis yearly per 212 men; in the general population of U.K. men between ages 65 and 69, rates have been reported to be slightly less than one in 200 per year.


"This myth about testosterone replacement therapy being linked to prostate cancer has been rooted deep in medical consciousness for over 60 years," said study co-author, Dr. Malcolm Carruthers, medical director at the Center for Men's Health in London. "But this paper says no, testosterone treatment is actually good for the prostate, not bad."


The study was published online June 6 in the Journal of Sexual Medicine.


Aging men sometimes experience "andropause"

Testosterone levels vary greatly among men, but generally tend to drop with aging, sometimes causing them to experience a so-called "andropause."


But unlike female menopause, which happens to all women as they age, not all men lose testosterone as they age, and the condition can also be overlooked, since the drop in hormone is gradual.  


According to the Mayo Clinic, however, by age 70, a man's testosterone level can drop by as much as 50 percent.


With the drop, men can experience a number of symptoms, including reduced sexual desire, fatigue, depression, bone loss and increased body fat.


Testosterone replacement therapy can reverse these symptoms.


"Evidence is rapidly accumulating that, not only is testosterone treatment important in maintaining a man's vitality and virility over the age of 50," Carruthers said, "but also in the treatment of a wider range of serious physical and mental illnesses."


But that may not always be the case when it comes to men who have already been treated for prostate cancer, according to Dr. Paul Nguyen, a radiation oncologist at Dana-Farber Cancer Institute in Boston.


"About 230,000 men a year are diagnosed with prostate cancer, and for those who have low testosterone after treatment, whether it's safe to treat them with testosterone remains a big issue," he said.


Testosterone treatment could improve quality of life

Researchers looked at 1,365 men participating in the ongoing U.K. Androgen Study. The men were treated with testosterone for at least three months for up to 20 years.


The researchers calculated that for every 10 men taking testosterone for 21 years, one would develop prostate cancer. In most cases, the cancer was detected with a test of prostate-specific antigen (PSA), a protein that suggests the presence of prostate cancer when found at high levels.


Based on study results, the researchers said that testosterone treatment is safe when carefully monitored.


As always, a larger study with longer follow-up would make doctors feel even more confident, Nguyen said. But he added the study was reassuring because of its size.


"For people with low testosterone who are thinking about getting treatment, this study helps to reduce the concern," Nguyen said.


"So, it gives them the freedom to pursue this treatment, which can improve their quality of life."


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