More than one therapy may be needed for the development of a reversible male contraceptive method, according to a proof-of-concept study being presented Monday, June 4, at The Endocrine Society’s 89th Annual Meeting in Toronto.

Previous research has shown that injections of testosterone in men who have normal levels of the male hormone suppress their sperm production. However, it takes weeks for the experimental drug therapy to become effective. The new study showed that use of a second physical agent given early during testosterone injections improves contraceptive effectiveness, said Dr. Christina Wang, lead author. Wang is Program Director of General Clinical Research Center at Los Angeles BioMedical Research Institute, the research arm of Harbor-UCLA Medical Center.

This study is the first, according to Wang, to show the contraceptive effects of short-term mild heat application to the testes, either alone or combined with testosterone injections in men. Wang and her co-workers previously tested the concept only in animals.

In this 18-week study, Wang’s group treated 54 healthy male volunteers in one of three ways. One group of men received a testosterone injection in a muscle every six weeks. The second group submerged their scrotum in warm water (109.3 degrees Fahrenheit) for 30 minutes every day for six consecutive days. The final group had a combination of the two treatments. The men were checked after the transient heat exposure to the testis and there were no side effects.

In men who received combination therapy, sperm production decreased as early as three weeks after the initial treatment and stayed suppressed until the end of treatment. Neither single treatment was effective as quickly as the combined treatment. Also, the researchers showed that heat plus testosterone was a reversible contraceptive; sperm counts recovered after treatment stopped.

Men will be relieved to hear that heat therapy is not intended to be a method of contraception. Wang said they hope to use this method to learn what molecular pathway controls the suppression of sperm production after the application of heat and/or testosterone.

“This will allow the discovery of novel therapies for male contraception without heat application or hormones,” she said.

The study received financial support from the Contraceptive Research and Development Program through funding from the Gates Foundation and the U.S. Agency for International Development (USAID).

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