1. To evaluate the bone turnover (activity of bone cells) subjects will have blood and urine collected for measurement of biochemical markers of bone turnover (chemicals in the blood and urine that reflect the activity of bone cells) measured before and at 1, 2, 3, 6, 9, and 12 months. Subjects will have 10 mL (about 2 teaspoons) of blood drawn at each of these visits.