1. Department of Endocrinology and Metabolism, Odense University Hospital, Odense, Denmark.
2. The Danish Twin Registry, Epidemiology, Institute of Public Health, University of Southern Denmark, Odense, Denmark.
3. Faculty Division Rikshospitalet, University of Oslo, Oslo, Norway.
4. Division of Mental Health, The Norwegian Institute of Public Health, Oslo, Norway.
5. Department of Clinical Chemistry, Ulleval University Hospital, Oslo, Norway.
6. Institute of Regional Health Services Research, University of Southern Denmark, Odense, Denmark.
7. Department of Medical Genetics, Rikshospitalet University Hospital, Oslo, Norway.