1 Division of Endocrinology and Diabetes, The Children's Hospital of Philadelphia, Department of Pediatrics, The University of Pennsylvania, Philadelphia, Pennsylvania, USA.
2 Division of Endocrinology, The Hospital for Sick Children, Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada.
3 Department of Endocrine Neoplasia and Hormonal Disorders and Department of Pediatrics-Patient Care, University of Texas MD Anderson Cancer Center, Houston, Texas, USA.