Dr Helen O'Neill: The woman who is changing what we know about hormones

Dr Helen O'Neill is many things: a mirror twin, an associate professor in reproductive and molecular genetics at UCL, and also the co-founder and chief executive of Hertility, the at-home hormone testing company which is changing what we know about infertility: the company has built up a database of 700,000 people whose responses to its health survey may shed new light on its causes. Meanwhile,…