Testosterone
As men age, their ability to
produce testosterone declines. As this stage is similar to
female menopause it is less subtle. Also, some men's production
of LH decreases with aging, which lowers testosterone production.
Moreover, a protein that binds up and holds onto testosterone
called sex hormone binding globulin (SHBG) increases in older
men. This reduces the amount of free (unbound) testosterone
in the blood that is available to tissues, such as muscles.
Aging also causes changes in the daily cycle of testosterone
production. For example, younger men show a peak of testosterone
in the morning, but this finding is blunted in older men.
The decrease in testosterone production as men age and symptoms
associated with testosterone deficiency are sometimes referred
to as andropause.
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