Among older men, there is a direct association between certain testosterone levels and sexual activity and desire, according to results of two studies.
Both studies were published in the Journal of Clinical Endocrinology & Metabolism.
The first study was a cross-sectional analysis of 788 patients from the Testosterone Trials (TTrials) who were aged at least 65 years. According to Glenn R. Cunningham, MD, study author, the TTrials were funded by the National Institute of Aging and were designed to determine if testosterone treatment improves symptoms and signs of testosterone deficiency in older men.
For the study, Dr. Cunningham, Peter J. Snyder, MD, principal investigator of the TTrials, and colleagues enrolled patients who had sexual dysfunction, diminished vitality and/or disabled mobility, and a mean total testosterone value of <275 ng/dL during screening visits before randomization.
No interventions were performed on these patients.
Among those enrolled, 470 were tested for sexual function, 474 for vitality and 388 for physical function.
Main outcome measures were question 4 of the Psychosocial Daily Questionnaire (PDQ-Q4), the FACIT-Fatigue Scale and the 6-minute walk test.
Dr. Snyder and colleagues observed positive and independent associations between baseline serum total testosterone (TT) and free testosterone (FT) levels and measures of sexual desire (TT, P=.034; FT, P=.02), erectile function (TT, P=.004; FT, P=.005) and sexual activity (TT, P=.024; FT, P=.014). However, there were no associations between these metrics of sexual health and estradiol and sex hormone-binding globulin levels.
Furthermore, there were also no associations between these hormone levels and ACIT-Fatigue, PHQ-9 Depression or Physical Function-10 scores, or gait speed.
“The main take-home message is that in older men who have low testosterone levels, we were able to show associations between total and free testosterone levels and different measures of sexual function,” Dr. Cunningham, who is professor of medicine at Baylor College of Medicine in Houston, said in an interview with Endocrinology Advisor.
“I think this is a finding that people have thought is likely, but it becomes less certain when you deal with older men who have the effects of aging and other possible causes for a lot of the symptoms.”
Interpreting the Data
According to Dr. Cunningham, these data from the TTrials are not the final answer. “The final answer will be if we are able to show that testosterone treatment does help these symptoms [of testosterone deficiency], particularly in older people,” he said. “That is going to be the factor that will determine [its effect on] clinical practice.”
Dr. Cunningham added that he and fellow researchers believe that these trials, which feature the largest number of subjects studied in a testosterone trial to date, will definitely show whether testosterone treatment is efficacious in older men who have low testosterone.
“That, in itself, will be quite important,” he said. “If we are able to show that, it will help to justify the use of testosterone treatment in older men. If not, of course, the opposite will be true. So people should look to the future, as these results get analyzed and published.”
Effect of Serum Testosterone on Sexual Function
A second study, a longitudinal analysis of the CHAMP trial, similarly examined the effect of testosterone levels on sexual function in older men.
Benjumin Hsu, MPH, of the University of Sydney in Sydney in New South Wales, Australia, and colleagues looked at 1,226 men aged at least 70 years.
They found that although baseline hormones, including testosterone, dihydrotestosterone, estradiol and estrone, were not associated with sexual function, declines in serum testosterone at 2 years predicted change in sexual activity and desire, but not erectile dysfunction. Specifically, for each standard deviation decrease of 1 in testosterone, there was increased risk for further decline in sexual activity (multivariate-adjusted OR=1.23; 95% CI, 1.12-1.37).
Similar associations were observed between changes in serum testosterone and declines in sexual desire, but not erectile dysfunction, according to the results.
“While these observational findings cannot determine causality, the small magnitude of the decrease in serum [testosterone] raises the hypothesis that reduced sexual function may reduce serum [testosterone] rather than the reverse,” Hsu and colleagues wrote.