People profoundly deficient in human growth hormone (HGH) due to a genetic mutation appear to live just as long as people who make normal amounts of the hormone, a newly released study shows. The findings suggest that HGH may not be the "fountain of youth" that some scientists have suggested. "Without HGH, these people still live long, healthy lives, and our results don't seem to support the notion that lack of HGH slows or accelerates the aging process," says Roberto Salvatori, M.D., associate professor in the Department of Endocrinology at the Johns Hopkins University School of Medicine.