"One year of treatment with testosterone gel was associated with improvement in cognitive performance and a slowing of brain atrophy [deterioration]," the authors write. During the first nine months of the study-the period of time before the men began taking testosterone, plus the first three months of treatment, before it had time to take effect-brain volume decreased an average of -0.81 percent per year. In the second nine months, this decline slowed by 67 percent to an annual rate of -0.25 percent. "Because the protective effect of testosterone treatment on brain atrophy was observed in the absence of an appreciable anti-inflammatory effect, this protection may not be limited to MS, but may be applicable to those with non-inflammatory neurodegenerative diseases," including Amyotrophic lateral sclerosis or Lou Gehrig's disease, the authors write.

In addition, lean body mass (muscle mass) increased an average of 1.7 kilograms (about 3.74 pounds) during the treatment phase. Participants did not report any adverse effects, there were no abnormalities in blood tests taken during the trial and the men's prostate examination results remained stable.