A middle-aged man goes to see his doctor, complaining of a host of vague symptoms: He's lethargic, somewhat depressed and feeling a little anxious about his manliness.
Could he just need a boost of testosterone, the vital sex hormone produced by the testicles?
These days, watching commercials from drug companies might lead you to believe that testosterone replacement could be just what you need, but researchers say it's unclear whether the issues associated with aging — decreased sex drive, less energy, reduced muscle mass — are the result of low testosterone or other factors.
Often equated with youth, vigor and strength, testosterone is responsible for the development of the penis and testes; it also helps build muscle and bone density, maintain adequate levels of red blood cells and helps keeps men confident and vibrant.
But as men age, the amount of testosterone in the body gradually declines. After age 30, a decline of about 1 percent a year begins and continues throughout the rest of a man's life.
Perspectives on treating 'low T'
There's substantial debate over whether decreasing testosterone levels need to be treated. Most experts say testosterone is about as effective as anti-wrinkle face cream when used to reverse the effects of aging.
Test results are hit or miss: Blood tests for testosterone are so unreliable — and saliva tests are worse — that the federal Centers for Disease Control and Prevention has launched the "Hormone Standardization Project" to improve the accuracy and standardization of the lab data.
Nor can doctors diagnose a condition using a single measurement, because lab results vary and levels of testosterone tend to fluctuate throughout the day. The highest levels of testosterone are generally in the morning.
Meaning of "low" and "normal" is unclear: Doctors don't exactly know what "low" is. "Normal" testosterone levels for any age are over 300 nanograms per deciliter. But the healthy range is large and spans between 250 and 1,100 nanograms per deciliter, said Neil Goodman, chairman of the hormone and reproductive medicine committee for the American Association of Clinical Endocrinologists.
"In general, if it's under 200, the guy really has a problem that needs to be worked on," said Goodman, a professor of medicine at the University of Miami. "It's the 200 to 300 range where no one can agree whether the symptoms are related to testosterone," said Goodman.
(Some men's bodies can't produce enough testosterone because their testes may be damaged or pituitary glands have been destroyed by infections or tumors. Chronic illness, stress, and alcoholism can also cause low testosterone. In these cases, prescription testosterone patches, injections or topical gel can help a man maintain strong muscles and bones and increase his sex drive.)
Replacement therapy to deal with expected, age-related testosterone decline is unproven: Testosterone therapy is still a "scientifically unproven method" for preventing or relieving the physical and psychological changes that men with age-appropriate testosterone levels experience later in life, according to a report by the Institute of Medicine. The Food and Drug Administration has not approved testosterone use — or any over-the-counter products — for those who want to improve their strength, athletic performance, physical appearance or to prevent aging.
Symptoms of age-related testosterone decline are vague: "There is a lot of marketing directed at men who want to be more attractive to potential partners, more muscular and vital," said endocrinologist Bradley Anawalt, a professor and vice chairman of medicine at the University of Washington in Seattle."But if you ask any man whether he feels tired some of the time, is a little depressed and whether his sexual prowess isn't what it used to be, you'll likely get a 'yes' to at least one of those questions."
Treatment has potential side effects: In 2009, the FDA issued strong warnings on two testosterone gel treatments after receiving reports that the children who had been exposed to the products had genitalia enlargement or aggressive behavior. Many researchers believe that supplements can put men at greater risk for prostate cancer — or stimulate the growth of the cancer if it is already present — and perhaps even greater risk for stroke, because it increases the production of red blood cells.
Including irreversible testicular function in some cases: There's also the use-it-or-lose-it factor. Men who supplement with testosterone shut down their own factory. "The real risk to (those who supplement) is if it stops their own testes from working," said Goodman. "If you're taking it long enough, you don't get testosterone production or sperm back. The testes can atrophy, and it can have a serious effect on testicular function in the future."
Overall health can also affect testosterone levels
Testosterone levels are a function of aging and health, said Anawalt, chairman of the Endocrine Society's Hormone Foundation. Some impotent men, for example, suffer from circulatory problems, not low testosterone. "It does seem that men who are vital and healthy are much less likely to have declines in testosterone," he said.
"It's a difficult chicken and egg question: Is a healthy man vital because his testosterone levels are high? Or do testosterone levels contribute to declines in health? It's probably a little of both."
The reality of 'low T'
It's unclear if heavily marketed testosterone replacement can stem age-related declines in muscle, sex drive or energy.
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