He actually lost is three times, all of them in the original Dragonball (which would be pre-DBZ in terms of the anime).
The first time he had changed into an Oozaru and was rampaging when Puar turned into some scissors and cut it off, which turned him back to normal.
Later it grows back, but during the tournament at Fortuneteller Baba's his Grandpa Gohan (who is visting Earth temporarily from the otherworld) rips it off.
It grows back yet again, but at this point Kami uses his powers to remove it permanently so he doesn't turn into a huge monkey again and trample innocent people.