1. Division of Endocrinology, Diabetes, and Metabolism (M.C.G., A.R.C.), Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104;
2. Department of Biostatistics (A.M.A.), University of Washington, Seattle, Washington 98155;
3. Division of Endocrinology, Gerontology, and Metabolism (J.S.L.), Stanford University School of Medicine and Veterans Administration Palo Alto Health Care System, Palo Alto, California 94305;
4. Departments of Pathology and Biochemistry (R.P.T.), University of Vermont, Burlington, Vermont 05405