Pre-study visit. (about 1 hour long) On a screening visit, prospective subjects (and their parents) will be provided with a description of the proposed study. After all their questions have been answered, they will be given a copy of the permission/assent form to review and sign Subjects will then have their medical history and use of medications reviewed, including the use of non-prescription and herbal remedies. All subjects will be given a complete physical examination by a physician, including vital signs (blood pressure, heart rate, breathing rate, temperature, height and weight) and an assessment of pubertal development by Tanner stage. Breast development will be assessed by visual inspection. Pubic hair will be assessed by visual inspection. Testicular volume will be measured by direct comparison to orchidometer beads. Tanner Staging will be assessed by a gender appropriate physician. Blood will be drawn by needle stick for serum chemistries, liver function tests and a hematology panel; a portion will also be retained for DNA testing (approximately 2 teaspoons of blood total). Urine will be collected for a Urinalysis with Micro. Numbing cream may be applied to the site to minimize discomfort. A urine pregnancy test will be performed for females of child bearing age.