The Role of Testosterone
Starting at about age 30, testosterone levels drop by about 10 percent every decade. At the same time, another factor in the body called Sex Binding Hormone Globulin, or SHBG, is increasing. SHBG traps much of the testosterone that is still circulating and makes it unavailable to exert its effects in the body's tissues. What's left over does the beneficial work and is known as 'bioavailable' testosterone.
Andropause is associated with low ("bioavailable") testosterone levels. Every man experiences a decline of bioavailable testosterone but some men's levels dip lower than others. And when this happens these men can experience Andropausal symptoms.
These symptoms can impact their quality of life and may expose them to other, longer-term risks of low testosterone. It is estimated that 30% of men in their 50s will have testosterone levels low enough to be causing symptoms or putting them at risk.