Many studies have shown cross-sectional (and two small studies, longitudinal) declines in
total and/or free testosterone (T) levels, with age, in men. The extent to which decline in T is
the result of the aging process per se, as opposed to chronic illness, medication use, and
other age-related factors, remains controversial. The frequency with which aging leads to T
levels consistent with hypogonadism has also not been defined. These issues bear on the
potential use of T replacement in aging men, because aging and hypogonadism have, in …