1. Diabetes Centre, Isala, Zwolle, The Netherlands.
2. Department of General Practice, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands.
3. Department of Endocrinology, Academic Medical Centre, Amsterdam, The Netherlands.
4. Department of Internal Medicine, University Medical Center Groningen and University of Groningen, Groningen, The Netherlands.
5. Langerhans Medical Research Group, Zwolle, The Netherlands.
6. Department of Internal Medicine, Isala, Zwolle, The Netherlands.