1. University Department of Clinical Biochemistry (I.S.F., E.L., J.K., S.O.), Addenbrooke’s Hospital, Cambridge CB2 2XY, United Kingdom
2. Department for Human Genetics (K.V., J.W.M.C.), University of Leuven and Flanders Interuniversity Institute for Biotechnology, B-3000 Leuven, Belgium
3. Department of Endocrinology (R.S.), Great Ormond Street Hospital, London WC1N 3JH, United Kingdom
4. Department of Paediatric Gastroenterology (R.H.), Royal Free Hospital, London NW3 5NU, United Kingdom
5. Department of Endocrine Sciences (A.W.), Faculty of Life Sciences and Medical and Human Sciences, University of Manchester, Manchester M13 9PT, United Kingdom