Much of our current understanding of calcium metabolism rests in large part on a series of discoveries made by John T. Potts Jr. of the Massachusetts General Hospital. Potts is an internationally recognized authority on calcium metabolism and parathyroid hormone (PTH) in particular. In addition to his research, he carried an enormous leadership role, serving as both Chairman of Medicine and Physician in Chief of the MGH between 1981 and 1996. Watch the full interview for stories about working with Berson and Yalow, his approach to leading the MGH, and what has changed over his 56 years there.