Hormonal gel shows promise as reversible male birth control

Male hormonal contraceptives applied daily to the skin appear to reduce sperm production, according to a new study presented at the Endocrine Society annual meeting in Houston.

Very low sperm counts resulted for about 89% of men using a new combination of hormones, the study’s authors reported. They combined a transdermal gel containing testosterone and a gel containing 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 principal investigator Christina Wang, MD, of Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center. "Men can use transdermal gels at home-unlike the usual injections and implants, which must be given in a health care provider’s office."

In this preliminary study, the authors randomly assigned 99 healthy men to use one of three unidentified transdermal treatments every day for 6 months. The assigned treatment was either a gel containing 10 grams of testosterone plus a placebo gel, or the same testosterone gel plus a gel containing either 8 mg or 12 mg of Nestorone.

Fifty-six men completed at least 20 weeks of treatment and adhered to the study protocol. Only 23% of men who received testosterone alone obtained a sperm concentration less than 1 million sperm per mL, "a level that is compatible with very low pregnancy rates," Dr. Wang said. For the testosterone-progestin combinations, sperm counts reached that level in 88% to 89% of men, depending on the progestin dose.

In addition, complete absence of sperm occurred in significantly more men receiving combined testosterone and progestin than testosterone alone: 78% and 69% (8 mg and 12 mg of progestin, respectively) versus 23% for testosterone only.

"The combination of testosterone with Nestorone had few adverse effects," Dr. Wang said. "It warrants further study as a male contraceptive."

The Population Council, a nonprofit organization in New York, is the developer of Nestorone and supplied it for the study. Besins Pharma provided the testosterone gel.

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