In recent years, historians have turned their attention to the emergence of anti-aging medicine, suggesting that this interest group coalesced in the wake of widespread availability of recombinant human growth hormone (HGH) after 1985. We take a longer view of modern anti-aging medicine, unearthing a nexus of scientific, medical, and cultural factors that developed over several decades in the twentieth century to produce circumstances conducive to the emergence of this medical sub-specialty established on the premise of the anti-aging effects of HGH. Specifically, we locate these roots in earlier hormone replacement therapies and in the so-called life extension movement. We reveal the continual tension between, on the one hand, champions of a mainstream medical specialty and a field of biomedical research that aimed to improve health for the aged and, on the other hand, advocates who campaigned for medical endeavors to preserve midlife health in perpetuity, and even to extend the human lifespan. We also demonstrate that the two groups shared a belief in science to solve - or at least to ameliorate - the problems of aging. This commitment to science has been the hallmark of twentieth and twenty-first century prescriptions for living life longer and better.