Growth hormone treatment improves body fat distribution but also causes insulin resistance. Scientists have recently linked insulin resistance with special stores of fat in the muscles, which can be measured by magnetic resonance imaging (MRI). The researchers hypothesize that growth hormone will paradoxically reverse the linkage between muscle fat stores and insulin resistance. To assess this association and to investigate the cause(s), the researchers will measure muscle fat stores during growth hormone treatment. Other parameters linked to insulin resistance (glucose tolerance, blood markers, and body composition) will also be assessed. This study may lead to improved strategies for monitoring growth hormone therapy.