On multiple occasions, he said, he purchased hGH kits, which normally cost $1,600, and he confirmed that a $3,200 check he had written on July 20, 2004, was for a previous purchase of hGH.
That check was written a month after he was traded to the Orioles by the Kansas City Royals for promising pitcher Denny Bautista.
Dr. Gary Wadler, an associate professor at New York University School of Medicine and a member of the World Anti-Doping Agency, said hGH might or might not help in the recuperation process. But because it enlarges the muscles and is undetectable through urine testing, it is a popular drug for athletes.
Wadler has been a strong proponent of blood tests - something currently not utilized in baseball's testing program - to detect use of hGH.
"It should come as no surprise that growth hormone is a problem in baseball," Wadler said. "I cannot be persuaded on any logical basis for not having the [blood] test available."
There is currently no widely used test for hGH. A blood test does exist, but is not yet broadly available. It was used on a few hundred athletes at the 2004 Summer Olympics in Athens, Greece, and at the Winter Games earlier this year in Turin, Italy.
Baseball, however, contends there is no viable blood test available to detect hGH, but says MLB, working with scientists, is attempting to create a urine test.
Researchers are now working to come up with a version of the test that can be mass-produced. "Hopefully in the near future we will be able to test on a larger scale," said Frederic Donze, a spokesman for the World Anti-Doping Agency.
Congressmen who have followed the steroids issue closely since 2005's House Government Reform Committee hearings, are again watching the off-field baseball drama unfold.
"The absence of testing for hGH in baseball's drug policy is a huge loophole," said Rep. Henry A. Waxman, the top-ranking Democrat on the committee. "If the allegations in the Grimsley affidavit are true, players are still using this performance-enhancing drug."
First discovered in 1956, hGH is produced in the body by the pituitary gland, a small gland at the center of the brain. The substance can now be artificially synthesized and is available legally only by prescription.
Doctors typically prescribe it to excessively short children to help them reach normal height, and to AIDS patients who suffer from muscle wasting.