Injecting growth hormone into elderly people can dramatically reverse muscle loss-one of the most debilitating features of aging-in just six months, scientists reported Wednesday.

Human growth hormone, only recently made available in large quantities through genetic engineering techniques, can help restore strength and vigor to millions of elderly persons whose own production of the hormone has ceased, a team of researchers at the Medical College of Wisconsin found. They were assisted by scientists from several Chicago-area research institutions.

"Our study showed that six months of hormone treatment restored the amount of lean body mass that would be lost over two decades," said Dr. Daniel Rudman, professor of medicine at the Medical College.