Medical written November 1995 by Dr Richard Stanhope. Last updated September 2005 by Dr Richard Stanhope, Consultant Paediatric Endocrinologist, Great Ormond Street Hospital, London, UK. Psychological and behavioural characteristics last updated February 2004 by Dr O Udwin, Consultant Clinical Child Psychologist, West London Mental Health NHS Trust, London, UK and Dr A Kuczynski, Child Clinical Psychologist, South London & Maudsley NHS Trust, London, UK.