Male hormonal contraceptives contained in a gel applied daily to the skin have been found to reduce sperm production — showing promise as a potentially new form of reversible birth control for men.
In a presentation at the Endocrine Society's 94th Annual Meeting in Houston, researchers from the University of California-Los Angeles said the new hormone skin gel produced very low sperm counts in about 89 percent of the men treated with it. The gel treatment involved a combination of the male hormone testosterone and a new synthetic progestin called Nestorone.
"This is the first time that testosterone and Nestorone have been applied to the skin together to deliver adequate amounts of hormones that suppress sperm production," said lead researcher Dr. Christine Wang, with the UCLA Medical Center. "Men can use transdermal gels at home — unlike the usual injections and implants, which must be given in a healthcare provider's office."
Past studies of male contraceptives that combined testosterone and progestin used pills, implants or shots. The UCLA researchers noted progestin increases the contraceptive effectiveness of testosterone. Both hormones work together to turn off production of sperm.
For the new study, investigators randomly assigned 99 men to use one of three skin treatments every day for six months — a gel containing testosterone only, or one with testosterone plus Nestorone.
Nearly 9 in 10 men who received the testosterone-progestin combinations experienced a reduction in sperm counts to very low levels.
"The combination of testosterone with Nestorone had few adverse effects," Wang said. "It warrants further study as a male contraceptive."