Growth hormone (GH) is an underappreciated but important regulator of T cell development that can reverse age-related declines in thymopoiesis in rodents. Here, we report findings of a prospective randomized study examining the effects of GH on the immune system of HIV-1–infected adults. GH treatment was associated with increased thymic mass. In addition, GH treatment enhanced thymic output, as measured by both the frequency of T cell receptor rearrangement excision circles in circulating T cells and the numbers of circulating naive and total CD4+ T cells. These findings provide compelling evidence that GH induces de novo T cell production and may, accordingly, facilitate CD4+ T cell recovery in HIV-1–infected adults. Further, these randomized, prospective data have shown that thymic involution can be pharmacologically reversed in humans, suggesting that immune-based therapies could be used to enhance thymopoiesis in immunodeficient individuals.
Laura A. Napolitano, Diane Schmidt, Michael B. Gotway, Niloufar Ameli, Erin L. Filbert, Myra M. Ng, Julie L. Clor, Lorrie Epling, Elizabeth Sinclair, Paul D. Baum, Kai Li, Marisela Lua Killian, Peter Bacchetti, Joseph M. McCune