Largest placebo-controlled study to date finds
testosterone can address low libido, erectile dysfunction
Newswise, June 30, 2016—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 Guidelinerecommends 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.
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.
