NEW YORK (Reuters Health) - Lower testosterone levels are associated with worse sexual function (but not vitality or physical function) in older men with low libido, according to findings from the Testosterone Trials.
Sexual function, vitality, and physical function in men decline with aging, as do testosterone levels, but the relationship between these declines remains unclear.
Dr. Peter J. Snyder from the University of Pennsylvania in Philadelphia and colleagues investigated the relationship between sex hormones (total testosterone, free testosterone, estradiol, and sex hormone-binding globulin, or SHBG) in men age 65 or older with low testosterone and low libido.
Total testosterone and free testosterone were directly associated with sexual desire, erectile function, and sexual activity, whereas estradiol and SHBG were not.
In contrast, none of the hormones was significantly associated with vitality, gait speed, physical function, or depression, according to the December 30 online report in The Journal of Clinical Endocrinology & Metabolism.
"While statistically significant at the 0.05 level, the magnitude of the associations between baseline serum total and free testosterone and sexual desire, erectile function, and sexual activity was small, which is to be expected given the trial eligibility-driven restricted range of the values being correlated," the researchers note.
"Indeed," they say, "this issue, and the cross sectional nature of the comparisons reported here, likely contributed to the nonsignificant correlations between hormonal measures and trial outcome measures of vitality, depression, physical function, and gait speed."
"These findings suggest that the circulating free and total testosterone levels contribute more than estradiol or SHBG to the variation in some measures of sexual function in older men with low total testosterone," the investigators conclude.
The report did not address older men with low testosterone levels who did not complain of low libido, fatigue, poor physical functioning, or depression.
Dr. Snyder did not respond to a request for comments.
Ten of the 28 authors report financial relationships with various commercial enterprises, including eight with ties to AbbVie, which together with the National Institutes of Health partly funded the study.
J Clin Endocrinol Metab 2014
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