However, some studies have demonstrated thymic function in adults with HIV disease. Such function may be induced by positive feedback regulation of T cell production and the presence or absence of such function may play a determinant role in disease progression and response to highly active antiretroviral therapy (HAART). These studies suggest that the thymus is functional in many adults with HIV disease and that thymic function might be induced as a consequence of HIV-mediated peripheral T cell depletion. Growth hormone is a potent regulator of thymic function. This study will determine whether true thymic function can be induced in HIV infected adults, whether such induction is indeed prompted by growth hormone, and whether thymic function plays a role in sustaining the T cell compartment in the face of peripheral T cell depletion.