I would do a search if I were you. Tons of info here about this…
Do you mean the ball sack or the gonads themselves?
As was mentioned, the sack is easy to stretch… tugging, pumping, tons of ways. And it is permanent.
As for your actual ‘nads, well, diet and supplements can affect them. I think there is something called damiana (sp.?) that helps? Also, bodybuilders will know of something called clonodine or clodine or something like that… This is not permanent.
Like I said, a search will turn up tons of stuff… I am not too sure about spelling, but it has all been covered here before.
Cdr.BLop