The investigators plan to perform high resolution-peripheral quantitative computer tomography (HR-pQCT) using the XtremeCT device in future research studies to investigate the structural changes that occur during adolescence and young adulthood to attain peak bone mass (peak bone strength) and to evaluate the structural effects of anabolic treatments for osteoporosis. This preliminary study will establish the short term precision of the device in the populations that the investigators are likely to study and whether the new device is superior to their current pQCT device. It will also provide information on how measurements from the new device relate to bone turnover markers, which are one of their standard assessments of bone metabolism. They will also determine whether hormones that influence bone metabolism have specific effect on different components of bone structure. By providing data on the size and variability of differences in bone structure by gender and at important stages of skeletal development (end of longitudinal growth, peak bone mass and aging) this study will also form the basis of power calculations for future longitudinal studies.