1 The John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, International Centre for Life, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK. Electronic address: claire.wood@newcastle.ac.uk.
2 Department of Paediatric Endocrinology, Royal Victoria Infirmary, Newcastle University, Newcastle upon Tyne NE1 3BZ, UK.