1. 1Department of Clinical Chemistry, Maasstad Hospital, Rotterdam, The Netherlands
2. 2Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, The Netherlands
3. 3Department of Science, Maasstad Hospital, Rotterdam, The Netherlands
4. 4Department of Paediatrics, Leiden University Medical Center, Leiden, The Netherlands
5. 5Division of Endocrinology and Center for Endocrine Tumours, Department of Medicine, Leiden University Medical Center, Leiden, The Netherlands