1. The Center for Endocrinology, Diabetes, and Metabolism at Children's Hospital Los Angeles (C.M.S.R., D.D.J.), Keck School of Medicine of University of Southern California, Los Angeles, California 90027;
2. Departments of Medicine, Physiology, and Human Genetics (G.N.H.), McGill University, and Calcium Research Laboratory and Hormones and Cancer Research Unit, Royal Victoria Hospital, Montréal, Québec, Canada H3A 1A1;
3. Departments of Laboratory Medicine and Pathobiology, Medicine, and Genetics (D.E.C.C.), University of Toronto, Toronto, Ontario, Canada M5G IL5