Growth hormone may stimulate the production of T cells in HIV-infected patients, research at the Gladstone Institute of Virology and Immunology shows. T cells are the immune system cells that HIV attacks and destroys, leaving patients without defenses against the opportunistic infections of AIDS. Laura Napolitano, MD, lead investigator of the study, presented the research on July 11 at the 14th International AIDS Conference here in Barcelona. Napolitano is a staff research investigator at Gladstone and UCSF assistant professor of medicine. "Finding a way to stimulate the thymus to produce T cells would help HIV-infected patients to preserve and restore their embattled immune systems," Napolitano said. This study is the first to show that human thymic function can be significantly enhanced by growth hormone therapy to produce new T cells.
Results of the study were published in the May issue of the journal AIDS.
In the study, the researchers gave five HIV-infected male patients daily doses of growth hormone. After six months, the size of the thymus and the number of new T cells circulating in the blood increased significantly.
"The degree of change in the thymus was remarkable," Napolitano said. "Over the past five years, we have studied thymic function in more than four dozen similar patients who did not receive growth hormone, and we have never seen such striking changes in the thymus."
However, growth hormone therapy is not yet ready to be prescribed to stimulate immune function in HIV-infected patients. The study was small, and two of the five patients in the study experienced adverse effects of growth hormone therapy. Potential side effects include the development of diabetes, bone pain, swelling of the arms and legs, abnormal bone growth and carpal tunnel syndrome.
Additionally, this preliminary study was limited in its scope and was not designed to examine whether growth hormone actually improved the health status of the patients.
"The results of the current study are preliminary, but give us hope that we may be able to provide therapies to stimulate thymic function and T-cell production in individuals infected with HIV," concluded Napolitano.
"Additional studies need to be completed before we can conclude that growth hormone therapy provides benefit to the immune system of HIV-infected patients," Napolitano said. "We need to establish that the benefits of therapy outweigh the risks."
To address these concerns, Napolitano, along with principal investigator Joseph "Mike" McCune, are now enrolling a larger study that will directly compare HIV-infected patients on and off growth hormone for a longer period of time and with a larger number of tests.
