Low testosterone levels and decline in physical performance and muscle strength in older men: Findings from two prospective cohort studies

Laura A. Schaap, Saskia M.F. Pluijm, Dorly J.H. Deeg, Brenda W. Penninx, Barbara J. Nicklas, Paul Lips, Tamara B. Harris, Anne B. Newman, Steve B. Kritchevsky, Jane A. Cauley, Bret H. Goodpaster, Frances A. Tylavsky, Kristine Yaffe, Marjolein Visser