In middle-aged and older men with low testosterone levels, testosterone replacement therapy lasting a year or more was safe and caused no evidence of prostate disease, a new study found. The results will be presented Monday, June 16, at The Endocrine Society’s 90th Annual Meeting in San Francisco.

Prostate cancer is a concern regarding testosterone therapy in elderly men, along with the possibility of blood clots, said study coauthor Farid Saad, PhD, of Bayer Schering Pharma in Berlin. “There is no evidence that testosterone induces prostate cancer, but once a prostate cancer has developed, testosterone treatment will stimulate its growth,” he said.

For these reasons, men receiving testosterone treatment get closer medical surveillance than older men in general, he said. Also, Saad said doctors can adjust the dose to manage the risk of blood clots. Clots may occur because testosterone can overstimulate the formation of red blood cells. Furthermore, in recent years, The Endocrine Society and other organizations developed clinical practice guidelines designed to enhance the responsible and safe use of testosterone treatment in men with low testosterone.

Saad and his co-workers used these guidelines in treating their study subjects, he said. All 95 men in the study (ages 34 to 69 years) were hypogonadal, meaning their body does not produce enough testosterone and symptoms have resulted. Possible symptoms include diminished sex drive, erectile dysfunction, increased fat, and decreased muscle mass.

Patients received hormone replacement that restored testosterone levels to the normal range but did not exceed the upper limit, Saad said. Treatment used a slow-release, injectable form of the hormone (testosterone undecanoate) that is not yet available in the United States. Thirty men had testosterone treatment for 18 months; 51 men, for 15 months; and the remainder, for 12 months.

The researchers measured patients’ prostate volume and prostate-specific antigen (PSA), measures of prostate function. Increased PSA levels may indicate an enlarged prostate, inflammation of the prostate (prostatitis), or prostate cancer. Neither PSA nor prostate volume greatly increased due to testosterone treatment, according to Saad.

The investigators administered a hematocrit blood test to measure the number of red blood cells. Twelve men, all younger than 57, had hematocrit values above normal at some point in treatment, but all returned to normal without intervention, he said. Hemoglobin, a component of red blood cells, increased but not above the upper limit of normal, study data showed.

“If elderly men have a deficiency of testosterone, it is acceptably safe to treat them with testosterone as long as guidelines are followed,” he said. “But longer-term studies are needed.”

Researchers from The Netherlands and Germany collaborated on these studies. Study participants received treatment in a hospital clinic in Bremerhaven, Germany, which provided free care and testosterone through the German social health care system.

Saad is an employee of Bayer Schering, which makes a brand of testosterone undecanoate, and he contributed to the study design.

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Founded in 1916, The Endocrine Society is the world's oldest, largest, and most active organization devoted to research on hormones and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 14,000 scientists, physicians, educators, nurses and students in more than 80 countries. Together, these members represent all basic, applied, and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Md. To learn more about the Society, and the field of endocrinology, visit our web site at www.endo-society.org.