Older men with low testosterone levels showed improved bone density and strength, as well as reduced anemia, after one year of testosterone therapy, according to a new study conducted at Yale and other sites. The therapy had no impact on cognitive function, however, and may worsen plaque in coronary arteries, said the researchers.

The results of the four trials were published online Feb. 21 in two journals, JAMA and JAMA Internal Medicine.

The studies, known as the TTrials, are the largest trials to examine the efficacy of testosterone treatment in men 65 and older whose testosterone levels are low due to age. At 12 study sites across the country, 790 participants were given testosterone gel or a placebo applied daily to the skin. Over a year, investigators measured the effects of testosterone on four areas: anemia, bone density and strength, cardiovascular health, and cognitive function.

The findings were mixed:

• Anemia trial: After one year of treatment, 54% of the men with unexplained anemia and 52% of those with anemia from known causes had clinically significant increases in hemoglobin (red blood cell) levels, compared with 15% and 12%, respectively, of those in the placebo group.
• Bone trial: After one year, participants significantly increased volumetric bone mineral density – a marker of fracture risk – and estimated bone strength compared to controls. These results were greater in the spine than hip.
• Cardiovascular trial: The study found that the volume of non–calcified plaque – a build–up within the walls of blood vessels in the heart – increased significantly more in the testosterone–treated group compared to controls. The plaque was measured by coronary computerized tomographic arteriography, a type of heart scan.
• Cognition trial: After one year, there was no significant change in either the treatment or the placebo group in cognition, as measured by verbal memory, visual memory, executive function, and spatial ability.

The findings are the second set of results from the long–term TTrials, which demonstrated the benefit of testosterone therapy on sexual function in older men with low testosterone in a report published last year.

“Looking globally at testosterone therapy, the strongest evidence is for sexual function,” said Dr. Thomas Gill, the Humana Foundation Professor of Medicine and a lead author. The latest studies demonstrate that if a man with low serum testosterone is going to be prescribed testosterone for diminished sexual function, he may have some additional benefits on hemoglobin levels and bone density, Gill noted.

While the outcome of the cardiovascular trial raises concern, he said, a larger and longer study would be needed to determine the clinical significance of the findings.

The TTrials were conducted at 12 additional medical centers, including Albert Einstein College of Medicine, Baylor College of Medicine, Brigham and Women’s Hospital, Harbor–UCLA Medical Center, University of Alabama at Birmingham, Northwestern University Feinberg School of Medicine, Puget Sound Health Care System, University of California at San Diego School of Medicine, University of Florida School of Medicine, University of Minnesota School of Medicine, University of Pennsylvania, and University of Pittsburgh School of Public Health.