Washington, DC--Older men with low libido and low testosterone levels showed more interest in sex and engaged in more sexual activity when they underwent testosterone therapy, according to a new study published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism.
The study is the largest placebo-controlled trial in older men conducted on the subject to date. The sexual function study is part of the Testosterone Trials, a series of seven studies examining the effectiveness of hormone therapy in men who are 65 or older, who have low testosterone levels and are experiencing symptoms of testosterone deficiency. The research is supported primarily by the National Institutes of Health.
Testosterone is a key male sex hormone involved in maintaining sex drive, erectile function and sperm production. The Endocrine Society's Clinical Practice Guideline recommends using testosterone therapy to treat men with symptoms of androgen deficiency and low levels of testosterone. Androgen deficiency occurs when a man has consistently low levels of testosterone and resulting symptoms such as sexual dysfunction.
In the past 15 years, use of testosterone therapy has rapidly expanded among men. Testosterone levels decline as men age, and some men develop low testosterone levels and symptoms. Since 2000, the number of men beginning testosterone therapy has almost quadrupled in the United States, according to a 2014 study published in The Journal of Clinical Endocrinology & Metabolism.
"Our findings indicate low testosterone is one cause contributing to reduced libido and erectile dysfunction in older men," said the study's first author, Glenn R. Cunningham, MD, of Baylor College of Medicine and Baylor St. Luke's Medical Center in Houston, TX. "Men experiencing these symptoms should be evaluated for testosterone deficiency."
The study was designed to investigate the effectiveness of testosterone therapy. It was not large enough or long enough to address issues related to cardiovascular events or clinical prostate cancer.
The placebo-controlled, double-blinded trial examined the effect of testosterone therapy on sexual function in a group of 470 men. The men were enrolled in the study through 12 academic medical centers. The participants were at least 65 years old and had low testosterone levels, based on the average results of multiple tests. All of the men had a heterosexual partner.
During the year-long study, the men were assigned to receive either testosterone gel or a placebo applied to the skin. The participants answered questionnaires about sexual function at the outset and every three months during the 12-month study.
The men treated with testosterone therapy displayed consistent improvement in libido and in 10 of the 12 sexual activity measurements, including frequency of intercourse, masturbation and nighttime erections. In comparison, men who received the placebo did not change their questionnaire responses significantly over the course of the year-long study.
"For symptomatic older men with low testosterone levels, testosterone therapy led to consistent improvement in most types of sexual activity," Cunningham said.
Other authors of the study include: Alisa J. Stephens-Shields, John T. Farrar, Denise Cifelli, Laura K. Gallagher, Bret Zeldow, Xiaoling Hou, Susan S. Ellenberg and Peter J. Snyder of the University of Pennsylvania's Perelman School of Medicine in Philadelphia, PA; Raymond C. Rosen of New England Research Institutes, Inc., in Watertown, MA; Christina Wang and Ronald S. Swerdloff of Harbor-University of California at Los Angeles Medical Center and Los Angeles Biomedical Research Institute in Torrance, CA; Shalender Bhasin and Shehzad Basaria of Brigham and Women's Hospital, and Harvard Medical School in Boston, MA; Alvin M. Matsumoto of the Department of Veterans Affairs Puget Sound Health Care System and the University of Washington School of Medicine in Seattle, WA; J. Kellogg Parsons of the University of California, San Diego in San Diego, CA; Thomas M. Gill of Yale School of Medicine in New Haven, CT; Mark E. Molitch and David Cella of Northwestern University's Feinberg School of Medicine in Chicago, IL; Elizabeth Barrett-Connor of the University of California, San Diego School of Medicine in La Jolla, CA; Jane A. Cauley of the University of Pittsburgh in Pittsburgh, PA; Jill P. Crandall and Vafa Tabatabaie of Albert Einstein College of Medicine in the Bronx, NY; Kristine E. Ensrud of the Minneapolis VA Health Care System in Minneapolis, MN; Cora E. Lewis of the University of Alabama at Birmingham in Birmingham, AL; Marco Pahor and Stephen Anton of the University of Florida in Gainesville, FL; and Susan J. Diem of the University of Minnesota in Minneapolis, MN.
The research was supported by a grant from the National Institutes of Health's National Institute on Aging, with additional support from the National Heart, Lung, and Blood Institute; the National Institute of Neurological Disorders and Stroke; the National Institute of Child Health and Human Development; the Claude D. Pepper Older Americans Independence Centers, the Department of Veterans Affairs Puget Sound Health Care System; and the National Institute of Diabetes and Digestive and Kidney Diseases. Pharmaceutical manufacturer AbbVie, the maker of a testosterone gel called AndroGel, provided funding as well as the testosterone gel and placebo for the study.
The study, "Testosterone Treatment and Sexual Function in Older Men with Low Testosterone Levels," will be published online at http://press.endocrine.org/doi/10.1210/jc.2016-1645, ahead of print.
For more information on testosterone, visit the Hormone Health Network's website.
Endocrinologists are at the core of solving the most pressing health problems of our time, from diabetes and obesity to infertility, bone health, and hormone-related cancers. The Endocrine Society is the world's oldest and largest organization of scientists devoted to hormone research and physicians who care for people with hormone-related conditions.
The Society, which is celebrating its centennial in 2016, has more than 18,000 members, including scientists, physicians, educators, nurses and students in 122 countries. To learn more about the Society and the field of endocrinology, visit our site at http://www.endocrine.org. Follow us on Twitter at @TheEndoSociety and @EndoMedia.
The Journal of Clinical Endocrinology & Metabolism