Department of Pediatrics, Montreal Children's Hospital, McGill University, Montreal, Quebec, Canada. Division of Bioinformatics and Biostatistics Pediatric Epidemiology Center, Department of Pediatrics, University of South Florida, Tampa. Division of Endocrinology, UPMC Children's Hospital, University of Pittsburgh, Pittsburgh, Pennsylvania. Department of Pediatrics, Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada. Linköping University Hospital, Linköping, Sweden. Division of Pediatrics, Department of Clinical and Experimental Medicine, Medical Faculty, Linköping University, Linköping, Sweden. University of Helsinki, Helsinki, Finland. Helsinki University Hospital, Helsinki, Finland.