1. Centre for Endocrinology, Diabetes and Metabolism (J.I., V.D., P.P., C.H.L.S., N.K., W.A.), School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, United Kingdom
2. Department of Paediatric Endocrinology (T.R.), Nottingham Children's Hospital, Nottingham University Hospitals National Health Service Trust, Nottingham NG7 2UH, United Kingdom
3. Department of Clinical Biochemistry (N.F.T.), King's College Hospital, University of London, London SE5 9RS, United Kingdom