Many bodily functions are controlled by hormones, chemical messengers produced by various glands. Testosterone is the principal male sex hormone. Produced primarily in the testicles, it is essential in stimulating the development of male sexual characteristics in boys at puberty. In men, it helps maintain muscle and bone strength as well as sexual drive and performance.
After the age of 30, the normal testosterone level declines slowly but steadily in men. In some men, testosterone production declines more rapidly than others, although there is no sudden change comparable to menopause in women.
Today, men are living longer and many are seeking ways to improve their quality of life. Regular exercise, avoiding obesity, not smoking, limiting alcohol consumption, and eating a balanced diet have all been shown to be effective at maintaining good health.
Some believe that restoring testosterone to ‘youthful levels’ may reverse some of the changes of age: improving sexual function, muscle strength, bone health, and even, mood and mental function in aging men. Pharmaceutical companies, the media, and some physicians have promoted these possible benefits, suggesting that as much as a third of all men are testosterone deficient and requiring treatment. Annual sales of testosterone replacement treatments have increased dramatically in North America. This explosion in testosterone supplementation has occurred before science has answered fundamental questions regarding its safety and effectiveness.