This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Insulin resistance (IR) is associated with special stores of fat in muscle, which can be measured by MRI. Growth hormone (GH) treatment can also cause IR. In this study, we will determine how GH affects muscle fat stores in girls receiving GH for short stature, both during and without GH treatment. Assessments include analyses of muscle fat by MRI, insulin sensitivity, and body composition. Our studies are intended to help us understand how GH causes IR and may lead to ways to increase its safety and effectiveness.