Professor Gary Butler is a Consultant in Paediatric & Adolescent Medicine and Endocrinology at University College Hospital in London and holds an Honorary Personal Clinical. He has established an adolescent endocrine service at UCLH, and is the Chair of the ESPE Gender Dysphoria Working Group. In 2018, he was the host of the first ESPE Science Symposium on 'The Science of Gender'.; Professor Jeremy Kirk has published over 140 peer reviewed articles, chapters and books. He is a Consultant Paediatric Endocrinologist at Birmingham Women's and Children's Hospital NHS Foundation Trust, an Honorary Professor University of Birmingham and University of Wolverhampton, as well as Clinical Director NIHR Clinical Research Network (CRN), West Midlands.