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.

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 ...

But men are facing a disturbing global decline in their hormonal health, with one major study reporting a “substantial” drop in testosterone levels since 1987, at a rate of 1 per cent each year.

"The Sun" reports that according to studies conducted in 2006, 2007, and 2013 on both sides of the Atlantic, testosterone levels in young men are rapidly declining.

Dr. Nancy Nagpal, a gynecologist at Salubritas Med Center, explains what happens when there is less or more testosterone in the body and what should be its normal level in men and women.

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).