Narrator: It's a widely held belief that physical and, in some cases, mental abilities wane as we get older.
Vin Tangpricha, MD, PhD: …It's not clear whether or not that's just a normal aging process, or whether or not that's abnormal and can be reversed.
Narrator: Remaining virile is a top priority for many men—especially as they enter middle age.
Ian Kippen: …I'm obviously not as strong or fast as I was 20 years ago, but I try to keep fit.
Leon Furth: …I'm a little bit slower than I was when I was 25 but I've got a lot of stamina. I can still do a lot of things.
Narrator: In their search for answers, experts have begun examining the link between sexual hormone production and certain chronic disease states associated with aging.
Vin Tangpricha, MD, PhD: …Roughly, I would say about 25 percent of men over 45 may have low testosterone.
Narrator: In men, a lower than normal testosterone count can be associated with number of physical and mental dysfunctions like…
Chad Ritenour, MD: ……Decreasing sexual desire, maybe a loss of spontaneous erections, infertility is a big problem we see, testicular size decreasing.
…And then there's some less specific symptoms such as fatigue, just a loss of energy…
Narrator: Low testosterone levels have also been associated with decreased muscle mass, osteoporosis and metabolic syndrome—a condition that can often lead to diabetes.
Lifestyle modifications such as stress management and diet can often boost levels back up.
George Jordan: …I am 82 going on 65
Chad Ritenour, MD: …We know that obesity affects testosterone levels.
So, for example, putting someone on an exercise program a lot of times improves symptoms and may actually improve some testosterone levels.
Narrator: But in aging men when a low reading is associated with symptoms many doctors are now treating with "testosterone replacement therapy", or TRT, as a means of jacking levels back up.
Treatment can come by way of injections, patches or gels. Although results have been encouraging, there are certain risks. And data from long-term use is not yet available.
Chad Ritenour, MD: "…I think the current guidelines would suggest you need both the combination of symptoms and a low level before you initiate treatment.
Narrator: Once on treatment, patients must be carefully monitored for adverse effects such as a rare condition where the blood becomes overloaded with too many red blood cells.
Physicians must also be careful not to overdose. Higher than normal levels of testosterone have been shown to cause dangerous mood swings.
Vin Tangpricha, MD, PhD: …The testicles will atrophy and that when you stop the testosterone use they may not recover. And so, you in a way are going to commit yourself to a lifetime use of testosterone.
Narrator: That's one reason physicians may take a more conservative approach if a man merely has a low testosterone reading.
But for men with no other option, or who may face a higher risk from a life-threatening illness, doctors now MAY have a treatment that can potentially help many live longer more fulfilling lives.
For WebMD, I'm Damon Meharg.