Longitudinal studies in male aging studies have shown that serum testosterone levels decline with age (Harman et al 2001; Feldman et al 2002). Total testosterone levels fall at an average of 1.6% per year whilst free and bioavailable levels fall by 2%–3% per year. The reduction in free and bioavailable testosterone levels is larger because aging is also associated with increases in SHBG levels (Feldman et al 2002). Cross-sectional data supports these trends but has usually shown smaller reductions in testosterone levels with aging (Feldman et al 2002). This is likely to reflect strict entry criteria to cross-sectional studies so that young healthy men are compared to older healthy men. During the course of longitudinal studies some men may develop pathologies which accentuate decreases in testosterone levels.
As already indicated previously, testosterone levels, particularly bioavailable testosterone, fall with advancing age. This decline in testosterone availability may start to occur early in the forth decade but it usually becomes clinically manifest in the 50s and 60s. Although there is continuing debate about the best way to diagnose hypogonadism in the aging male, there appears to be a general consensus that symptomatic men with reduced levels of testosterone should be given a trial of testosterone therapy if there is no contraindication to do so (Bain et al 2007).

Saw palmetto: Uses, dosage, and side effects Saw palmetto is an extract from the berries of a type of palm tree. The berries have traditionally been used to ease urinary and reproductive problems. The extract is now used in herbal remedies to stabilize testosterone. Learn about its use, its effectiveness, the science behind the claims, and any side effects. Read now