The good news, this Christmas, is that researchers have found that a compound that acts the opposite way that growth hormones act can reverse some signs of aging. The bad news is that the same research suggests that people who take a growth hormone to stay young may be doing more harm than good. Science Daily reports that the research, conducted at the University of St. Louis, found that in studies involving mice, compound MZ-5-156 had positive effects on oxidative stress in the brain, improving cognition, telomerase activity and life span, while decreasing tumor activity. MZ-5-156 is described as a "growth hormone-releasing hormone (GHRH) antagonist." The researchers also found that MZ-5-156, like many GHRH antagonists, inhibited several human cancers, including prostate, breast, brain and lung cancers. It also had positive effects on learning, and reversed cognitive impairment in the aging mice.