The New York Yankees left-hander had been fingered in the Mitchell Report by former trainer Brian McNamee, who claimed that Pettitte had used HGH on "two to four" occasions.
Pettitte quickly admitted to receiving two injections in 2002 while recovering from injury, but revealed on Feb. 8 in a sworn affidavit that he injected himself once in 2004, shortly before undergoing season-ending elbow surgery.
"In 2004, when I tore the flexor tendon in my pitching arm, I again used HGH two times in one day out of frustration and in a futile attempt to recover," Pettitte said in his affidavit. "Unfortunately, I needed surgery on the arm later in the year. I regret these lapses in judgment."
Pettitte's lawyers, Jay Reisinger, Thomas Farrell and James Sharp, released word of the 2004 use in a statement.
"Andy had not previously mentioned this usage because he acquired the substance from his father, who had obtained it without Andy's knowledge in an effort to overcome his very serious health problems, which have included serious cardiac conditions," the statement said.
"Andy did not want his father, whom he deeply respects and loves, to be brought into this matter and sought to shield him from publicity. In both cases, Andy used HGH in a misguided effort to recover from injury."
More damaging was Pettitte's assertion in a sworn affidavit that Clemens, a seven-time Cy Young Award winner, confided in Pettitte that he was using HGH in 1999 or 2000, doing so in a conversation at Clemens' gymnasium in Memorial, Tex.
Clemens would later recant in a Spring Training 2005 conversation in Kissimmee, Fla., telling Pettitte that he had been speaking about his wife, Debbie's, HGH use. But Pettitte's statements were supported in another sworn affidavit provided by Pettitte's wife, Linda.
Clemens contends that Pettitte "misremembers" the context of the conversation.
"Andy Pettitte is my friend," Clemens said. "He was my friend before this. He will be my friend after this. I think Andy has misheard -- I think he misremembers our conversation."
Lanny Breuer, one of Clemens' attorneys, said that Pettitte's absence was surprising.
"He's not here, and I'd like to know why he's not here," Breuer said. "But people make mistakes. People forget."
Speaking to reporters at the team's training facilities in Tampa, Fla., Yankees manager Joe Girardi said that Pettitte has been excused from reporting to Spring Training until Monday, when the 35-year-old hurler is expected to address reporters.
"Andy has a great ability to focus," Girardi said. "We've all seen Andy, how he pitches in big games, and he has that look in his eyes. I could tell it when I was behind the plate. I can tell it when I talk to him. So I have a great feeling about it."
The rest of the Yankees' pitchers and catchers are set to report on Thursday.
Pettitte was originally scheduled to appear on Capitol Hill for Wednesday's hearing, titled "The Mitchell Report: The Illegal Use of Steroids in Major League Baseball, Day 2."
But, satisfied that they had answered all of the committee's questions truthfully, chairman Henry Waxman (D-Calif.) and ranking Republican Tom Davis (R-Va.) issued a statement excusing both Pettitte and former big league infielder Chuck Knoblauch.
Admitted steroids distributor Kirk Radomski was also excused, as he was expected to invoke his Fifth Amendment rights against self-incrimination.
Rep. Elijah Cummings (D-Md.) said that if he had to choose between Clemens and McNamee, he'd prefer to believe the testimony provided by Pettitte.
Rep. Waxman also lauded Pettitte for admitting his personal experiences with performance-enhancing drugs.
"Mr. Pettitte's consistency makes him a role model on and off the field," Waxman said.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.