By now you've likely seen the commercials. Fit-looking middle-age men telling you how they put on weight, had less energy, and were no longer the sexual tigers they were in their twenties -- until, that is, they started rubbing testosterone gel on their shoulder, upper arm, or abdomen.
Now they feel more like the men they used to be.
The commercials don't mention a 2009 study in the New England Journal of Medicine wherein a group of men on testosterone replacement therapy had more than four times the number of cardiovascular problems -- so many that the study had to be halted.
They also don't make clear how risky exposure to testosterone gel is for others -- female partners, children, even pets. The gel is actually notorious for transferring to others. It can cause excess hair to grow on women's faces and arms, deepen their voices, interrupt menstruation, and make them anxious and irritable. In children, exposure to testosterone gels and creams can cause premature puberty and aggression. And in pets, it can cause aggressive behavior and enlargement of the genitalia.
Commercials do mention other potential side-effects for the male user, calling them "rare," including swollen and painful breasts, blood clots in the legs, increased risk for prostate cancer, problems breathing during sleep (sleep apnea), change in the size and shape of the testicles, and a low sperm count. But you're not supposed to focus on the details. Instead, just think of the energy you'll have. The great sex you'll have. And the muscles. It will be a veritable second adolescence as your aging body bursts into new bloom.
Testosterone levels in men fall by only 1 to 2 percent a year after age 40.
Don't get me wrong. The medical experts interviewed for this article emphasized that low testosterone -- also known as hypogonadism or hypotestosteronemia -- is real for a slim percentage of men. They hastened to add, however, that a normal "T" level for one man may be low for another.
According to British Medical Journal (BMJ), the European Male Ageing Study has provided the best estimate of the prevalence of low T -- defined as a combination of sexual symptoms and measured testosterone level -- finding that only 0.1 percent of men in their forties, 0.6 percent in their fifties, 3.2 percent in their sixties, and 5.1 percent of men in their seventies would meet the criteria for the diagnosis.
Unlike menopause in women -- when estrogen levels plummet and stop almost completely -- testosterone levels in men normally fall by only 1 to 2 percent per year after age 40.
"Low T" is anything but inevitable. BMJ's Drug and Therapeutics Bulletin says that around 80 percent of 60-year-old men, and half of those in their eighties, have testosterone levels within the normal range for younger men. It concluded, "The evidence that an age-related reduction in testosterone levels causes specific symptoms is weak." The Food and Drug Administration (FDA) meanwhile has not approved testosterone use to improve strength, athletic performance, physical appearance, or prevent aging. And a 2004 report from the Institute of Medicine ("Testosterone and Aging: Clinical Research Directions") called TRT for age-related testosterone decline a "scientifically unproven method."
"A proportion of older men will predictably have testosterone concentrations below the normal range of healthy young men," wrote BMJ deputy editor Tony Delamothe, in a 2012 commentary. He added, "It seems a bit harsh to turn an age-related phenomenon into a disease, but that's what's happened."
In the age-old tradition of snake oil peddlers and traveling medicine shows, TRT is but the latest elixir from the fountain of youth. Offering a heady brew of hope and hype distilled at the drawing boards of advertising agencies, tubes of testosterone are the latest wares for the unwary.
So what is this Big T, anyway? Derived from cholesterol, testosterone is a steroid hormone -- called an androgen -- that causes the development and maintenance of masculine characteristics. It's mainly secreted by the testicles in males, although the adrenal cortex and ovaries in females also secrete testosterone -- though only about one-tenth the amount as in healthy males.
Interest in testosterone began when farmers of old first noticed that castrated animals were more docile than their intact peers. Ditto for castrated humans. For human males with intact gonads, testosterone increases during puberty. It deepens the voice, increases muscle growth, promotes facial and body hair, and spurs the sex drive. Testosterone also is associated with personality traits related to power and dominance.
Although Dr. Wyne has seen an increase in male patients asking about low testosterone, she hasn't seen an actual increase in the condition itself.
Testosterone levels fluctuate throughout the day, and are usually highest in the morning. They peak in the late teens to early twenties, after which they decline slowly, but steadily, as men age. Although there is no standard definition of "low" testosterone, a healthy range spans between 250 to 1,100 nanograms per deciliter of blood.
Questions inevitably arise: If even scientists don't agree on what, exactly, "low T" means, how can anyone diagnose it? At what point is it problematic? And, most importantly, how can you know whether you are a candidate for TRT?
"I am very cautious about committing someone for life to medication," said Dr. Kathleen L. Wyne, who directs research on diabetes and metabolism at Houston's Methodist Hospital Research Institute and serves on the Sex Hormone and Reproductive Endocrinology Scientific Committee for the American Association of Clinical Endocrinologists. "That does frustrate patients because they have heard about [Low T] from TV and friends."