1. Endocrine Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, U.S.A.
2. Section of Metabolic Analysis and Mass Spectroscopy, National Institute of Child Health and Human Development, Bethesda, Maryland, U.S.A.
3. Section of Diagnostic Nuclear Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, U.S.A.
4. Division of Hematology and Internal Medicine, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, U.S.A.
5. Nephrology Research Unit, Mayo Clinic and Mayo Foundation, Rochester, Minnesota, U.S.A.