Houston—Older men using “Low T” treatment will undoubtedly welcome this news from their pharmacist: Testosterone replacement therapy was found to increase their interest in sex and promote more sexual activity if they previously had low libido and low testosterone levels.

The study, touted as the largest placebo-controlled trial in older men conducted on the subject to date, was published recently in the Journal of Clinical Endocrinology & Metabolism.

The sexual function study is part of the National Institute of Health’s Testosterone Trials, a series of seven studies examining the effectiveness of hormone therapy in men who are 65 or older, have low testosterone levels, and are experiencing symptoms of testosterone deficiency.

The Endocrine Society's clinical practice guidelines recommend using testosterone therapy to treat men with symptoms of androgen deficiency and low levels of testosterone.

“Our findings indicate low testosterone is one cause contributing to reduced libido and erectile dysfunction in older men,” said the study’s lead author, Glenn R. Cunningham, MD, of Baylor College of Medicine and Baylor St. Luke’s Medical Center in Houston. “Men experiencing these symptoms should be evaluated for testosterone deficiency.”

While the study was designed to investigate the effectiveness of testosterone therapy, it was powered to address issues related to cardiovascular events or clinical prostate cancer, study authors point out.

For the study, 470 men were enrolled through 12 academic medical centers. Participants—who all had heterosexual partners—were at least 65 years old and had low testosterone levels, based on the average results of multiple tests.

The men were assigned to receive either testosterone gel or a placebo applied to the skin. At the outset and every 3 months during the 12-month study, they were asked to fill out questionnaires about sexual function.

Results indicate that the group 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. On the other hand, 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.

“In older men with low libido and low T levels, improvements in sexual desire and activity in response to T treatment were related to the magnitude of increases in T and estradiol levels, but there was no clear evidence of a threshold effect,” study authors conclude.

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