Dr. John P. Bilezikian, the Dorothy L. and Daniel H. Silberberg Professor of Medicine and Professor of Pharmacology at the College of Physicians & Surgeons, Columbia University is Chief of the Division of Endocrinology and Director of the Metabolic Bone Diseases Program at Columbia University Medical Center. Dr. Bilezikian received his undergraduate training at Harvard College and his medical training at the College of Physicians & Surgeons. He completed four years of house staff training (internship, residency and Chief Residency) on the Medical Service at Columbia Presbyterian Medical Center. Dr. Bilezikian received his training in Metabolic Bone Diseases and in Endocrinology at the NIH in the Mineral Metabolism Branch under the tutelage of Dr. Gerald Aurbach. Dr. Marcus is Professor-Emeritus, Stanford University, where he served on the full-time medical faculty for almost 25 years, before joining the Emeritus faculty in 2001. At Stanford, he was located at the Veterans Affairs Medical Center, Palo Alto California, where he served as Director of the Aging Study Unit of the Geriatrics Research, Education, & Clinical Center from 1982-2001. Dr. Marcus enjoyed a long career as a clinical investigator in the fields of bone and mineral metabolism and osteoporosis medicine. His own research interests included diagnosis and therapy of primary hyperpara-thyroidism, interactions of the parathyroid-vitamin D axis with estrogen, age-related changes in the growth hormone-IGF axis, effects of growth hormone replacement for older men and women, metabolic and musculoskeletal effects of resistance exercise in older men and women, adolescent bone acquisition, and osteoporosis therapeutics. Dr. Marcus' laboratory was a study site for many of the pivotal clinical trials in the osteoporosis field. These include the NIH Post-menopausal Estrogen/Progestin Interventions Trial (PEPI), Merck's Fracture Intervention Trial (FIT), Lilly's Multiple Outcomes of Raloxifene Intervention (MORE), and Lilly's registration trial of recombinant PTH(1-34) in the treatment of postmenopausal women with osteoporosis. In 2001. Dr. Marcus joined the US Affiliate of Eli Lilly & Company to support Lilly's program in Osteoporosis and Skeletal Medicine. From 2003 until his retirement from Lilly in 2008, Dr. Marcus was the lead physician for the Forteo team at Lilly. He has published more than 150 research papers, editorials, and reviews. Dr. Marcus served as President of the American Society for Bone & Mineral Research in 2000-2001. Dr. Michael A. Levine is Chief of Endocrinology and Diabetes and Director of the Center for Bone Health at The Children's Hospital of Philadelphia. Dr. Levine holds the Lester Baker Endowed Chair and is Professor of Pediatrics and Medicine at the University of Pennsylvania Perelman School of Medicine. Dr. Levine's research focuses on the genetic basis of disorders of bone and mineral metabolism and complements his clinical expertise in endocrine diseases that affect bone and mineral metabolism. His approach is to apply molecular and genetic tools to analyze the basis of altered hormone action, particularly in G protein-coupled signal transduction systems that affect growth and development. He has identified or contributed to the molecular basis of several inherited disorders of bone and mineral metabolism, including familial hypoparathyroidism, pseudohypoparathyroidism, cherubism, and the McCune Albright syndrome. His research interests now extend to the molecular events that control embryological development of the parathyroid glands and genetic modifiers of vitamin D action.