Once you start, your body begins shutting down natural production of the hormone, thinking it's no longer needed, he explains. This can lead to "shrinkage" of the testicles and a suppression of sperm production.

Broderick says finding a qualified doctor is key. Anti-aging is a new field and most doctors are not trained in hormone therapy, so they learn as they go from pharmaceutical reps and the latest published research. Testosterone replacement therapies often fall to physicians who specialize in "boutique medicine."

Once you find a physician, he or she should screen for prostate cancer before starting treatment. While studies have shown testosterone replacement therapies do not increase the likelihood of developing the cancer, they can encourage tumor growth if a patient already has it.

Broderick recommends getting blood work done every three to four months after beginning testosterone therapy. Men taking testosterone have increased levels of red blood cells, which can lead to complications with circulation, depriving areas of the body of oxygen.

On average, testosterone replacement therapy costs less than $40 a month. But many baby boomers, such as Freiburger, are using it as part of a more expensive holistic approach to staying healthy into their senior years -- and they say it's worth the cost.

"I would like to have as much quality of life and be as vital as I can as long as the Lord's going to have me on this earth," Freiburger says. "I'm going to take the time and financial resources to try to make that a reality."