1. Research Department of Infection and Population Health (S.C., A.J.C., C.T., N.F., P.S., C.H.M., A.M.J.), University College London, London WC1E 6BT, United Kingdom;
2. Department of Social and Environmental Health Research (W.M., K.R.M., K.W.), London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom;
3. Department of Clinical Biochemistry (B.G.K.), University Hospital S Manchester, Manchester M13 9WL, United Kingdom;
4. Cathie Marsh Institute for Social Research, School of Social Sciences (D.M.L.), The University of Manchester, Manchester M13 9WL, United Kingdom;
5. MRC/CSO Social and Public Health Sciences Unit (K.R.M.), University of Glasgow, Glasgow G12 8QQ, United Kingdom;
6. Kinsey Institute (J.B.), Indiana University, Bloomington, Indiana 47405;
7. Department of Clinical Biochemistry (A.M.W.), Royal Infirmary, Glasgow G4 0SF, United Kingdom;
8. Andrology Research Unit (F.C.W.W.), Manchester Centre of Endocrinology and Diabetes, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PL, United Kingdom