1. Institute of General Practice, Medical Faculty of the Heinrich-Heine-University Düsseldorf; Cochrane Metabolic and Endocrine Disorders Group; PO Box 101007 Düsseldorf Germany 40001
2. Herlev University Hospital; Department of Internal Medicine; Herlev Ringvej 75 Herlev Denmark DK-2730
3. University of Birmingham; Institute of Applied Health Research; Edgbaston Birmingham UK B15 2TT