Well men suffer a decline in testosterone starting at around age 35 and remarkably about 40% of men 45 and older have levels of testosterone that are viewed by the medical community as inadequate.

A single gene in the shorebird species known as ruffs controls the levels of testosterone in males, and this in turn affects ...

Vin Tangpricha, MD, PhD …Roughly, I would say about 25 percent of men over 45 may have low testosterone. Low testosterone levels have also been associated with decreased muscle mass ...

Testosterone is a hormone that affects male physical and mental health. It is produced primarily by the testicles but also by the adrenal glands and testosterone levels naturally decline with age ...

The study enrolled 88 men (60 years or older) with symptoms of hypogonadism and low testosterone levels (5.2–10.4 nmol/l in a single measure or 10.4–12.1 nmol/l in two consecutive measures).

in the blood of the birds that's able to regulate testosterone levels in males and rapidly break down the hormone normally associated with male dominance and aggression. "The species is crazy ...