What is it? A subdermal implant of a synthetic testosterone known as MENT placed in the upper arm, similar to hormonal implants used in female contraception. Injections of progestin may be necessary to supplement the hormones from the implant, however that has yet to be tested. Cost: The progestin injections are "relatively inexpensive," according to John Amory of the University of Washington, who is involved in developing this method. It's "impossible to say" what the implants will cost, he says, because a future pharmaceutical partner would be responsible for setting the price. Convenience: "You could argue that compliance is perfect with an implant, because unless it falls out, you're going to get the dose," Amory says. The MENT implants last for a year. If injections are needed, though, the method's convenience obviously decreases. Effectiveness: Past studies with MENT implants showed them to be around 80 percent effective, but "we're hopeful that these implants will be even better," Amory says. Reversibility: Just like with female hormone implants, you take it out and your fertility returns to normal. Status: The Population Council and the National Institutes of Health are developing a two-site, three-armed study to take place at the University of California, Los Angeles and the University of Washington. One set of subjects will receive only the MENT implant, one will get the implant and a single progestin injection, and one will get the implant and a progestin injection every three months. This is meant to determine if the progestin injections are necessary to suppress spermatogenesis, or if the implants can hold their own alone.

Julie Beck