The male hormone is involved in prostate growth, and previous studies have shown giving testosterone to men with advanced prostate cancer often makes the disease worse.
Concerns have risen over the growing trend of prescribing testosterone to older men to treat symptoms associated with declining testosterone levels, known as male menopause.
Testosterone levels among men decline with age, and in some men low testosterone levels may cause symptoms including depression, sexual dysfunction, decreased muscle mass, and lower bone density.
More than 1.8 million prescriptions for testosterone products were written in the U.S. in 2002, a 170% increase over the previous five years, according to pharmaceutical industry estimates.
But the risk of prostate cancer also rises with age, and researchers say more study is needed to determine if long-term testosterone replacement therapy is safe for the prostate.
Testosterone Therapy OK?
In the study, researchers examined the effects on the prostate of testosterone replacement therapy in 40 men. The men were aged 44 to 78 and had low testosterone levels.
The men received 150 milligrams of either testosterone or a placebo via injection every two weeks for six months.
Biopsies performed on prostate tissue taken from the men before and after the study showed testosterone levels within the prostate increased only slightly among the men who received testosterone therapy, although their blood levels of the hormone increased to normal levels.
"The prostate risks to men undergoing TRT may not be as great as once believed, especially if the results of the pretreatment biopsy are negative," writes researcher Leonard Marks, MD, of the UCLA School of Medicine, and colleagues in The Journal of The American Medical Association.
Researchers say larger studies are needed to determine the long-term safety of testosterone replacement therapy among older men.