They could have just asked any muscle-head....

The Birth control implant for men
Fine lead researcher and fertility expert Dr Peter Lui according to Kate Jones:

"Researchers have discovered a hormone that blocks sperm production, in much the same way as the female contraceptive pill prevents ovulation."

Later in the story, I read...

"The tests showed that by injecting synthetic testosterone into a man's body, hormone signals between the brain and the testes shut down to ultimately switch off sperm production. Researchers monitored the men's sperm count after they stopped the injections and found the effects of the contraceptive wore off between three and four months.

Some did not recover normal sperm levels until 24 months after treatment."

Wow! The hormone Lui discovered is Testosterone? I think this particular hormone was discovered by my 9th grade science teacher at the latest, or that guy who authored the 9th grade science book, or...wait a minute, not only is this story flawed temporally but ...

apparently brother Lui has discovered what is common knowledge to any muscle-head gym! If the urban myths are right, most will not ever recover their full potency as testes will shrivel and eventually lose the ability to function.