its male birth control
lowering testosterone is one way to do it only, you can also take test so your testies stop making babbies (pretty much like taking juice)
however both methods aren't as reliable, since if you have 99% efficiency, from 1 million sperm you would still have 10k sperm to account for, that could easily swim on and impregnate a potential egg
also wouldn't be surprised if we already have those kinds of hormones from feedstock