1. Department of Pediatrics, Medical University of Varna, Varna, Bulgaria
2. Department of Endocrinology, Abdominal Center, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
3. Department of Endocrinology and Metabolism, Amsterdam University Medical Center, Amsterdam, the Netherlands
4. Department of Medicine, Leiden University Medical Center, Leiden, the Netherlands
5. Department of Paediatric and Adolescent Medicine, Division of Paediatric Endocrinology and Diabetes, University of Lübeck, Lübeck, Germany