RIO DE JANEIRO, April 18 (Xinhua) -- Brazil's mixed martial arts middleweight champion Anderson Silva said Thursday he was against the use of hormone replacement therapy in the sport.

Chael Sonnen, Dan Henderson and Vitor Belfort are among competitors to have been given permission to use the treatment by the Ultimate Fighting Championship (UFC).

"I am no expert on the subject but the use of it ends up giving an athlete an edge over his opponent," Silva told Lancenet.

"It is unfair. I am not perfect but I have never needed hormone replacement therapy and I think that when you do need it, either you are too old to fight or you have used a prohibited substance for a long time that has stopped your body from producing what it should."

Silva, who has not lost a UFC bout since 2006, will defend his world title against American Chris Weidman in Las Vegas on July 6.