Prevalence, incidence and risk factors of testosterone deficiency in a population-based cohort of men: results from the study of health in Pomerania - Haring, R; Ittermann, T; Völzke, H; Krebs, A; Zygmunt, M; Felix, SB; Grabe, HJ; Nauck, M; Wallaschofski, H (The Aging Male, 2010)