1. Department of Clinical Biochemistry, University Hospital South Manchester, Manchester Academic Health Science Centre,
2. Research Department of Infection and Population Health, University College London, London WC1E 6BT, United Kingdom;
3. Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom;
4. Cathie Marsh Institute for Social Research, School of Social Sciences, and
5. Medical Research Council/Chief Scientist Office Social and Public Health Sciences Unit, University of Glasgow, Glasgow G4 0SF, United Kingdom; and
6. Kinsey Institute, Indiana University, Bloomington, Indiana 47405
7. Andrology Research Unit, Manchester Centre of Endocrinology and Diabetes, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PL, United Kingdom;