Leigh hooker Sean Penkywicz has accepted a two-year ban after testing positive for a growth hormone GHRP6.
Penkywicz, 33, who denies knowingly taking it was banned for two years in 2005 after testing positive for stanozolol, an anabolic steroid.
GHRP6, which is usually injected but is found in creams and gels, can reduce body fat and increase muscle mass.
UK Anti-Doping retested an initial negative sample from December 2014 to find the substance.
The former Wales international has now had his contract terminated by Leigh.
|Penkywicz at Leigh|
|The former Huddersfield man joined the Centurions from Halifax in 2012 and helped the club to the Championship title in 2014. He played his last game in April and had scored four tries in his nine appearances this season.|
"This really has hit me hard as I just can't understand it and I am now legally advised I need to accept a two-year ban, which essentially ends my career at a time when I was finding some of my best form," Penkywicz said in a statement.
"It is so frustrating and angers me to be told I have put something into my body when I know I haven't. I want to keep fighting but it is just making me ill and there simply is nothing more in the tank.
"I wished I could say I am sorry I have let everyone down, but I cannot as I have not knowingly injected myself with drugs."