Although it’s normal for testosterone levels to drop as men age, low testosterone can affect a man’s health. In many ways, testosterone is the stuff that makes men men. The rush of new testosterone in puberty builds muscle and bone, deepens the voice, and revs up the sex drive. Throughout a man’s life, testosterone maintains his male characteristics.

Testosterone levels decline steadily after age 40. The decline is relatively small, at an average rate of about 1% to 2% percent per year. By middle age and older, virtually all men experience some decline in testosterone -- but only a small percentage of aging men have levels far below those considered normal for their age.

Is this low testosterone part of normal aging -- or a medical problem that needs treatment?

“If a man doesn’t have symptoms, you shouldn’t even test [for low testosterone],” says Karen Herbst, MD, PhD, an endocrinologist with the University of California at San Diego. “There’s no proof that treating low testosterone in the absence of symptoms has any benefits. But in men with symptoms of [low testosterone], many of them will get a benefit from treatment.”

What is Low Testosterone?

Low testosterone is defined as less than 300 nanograms per deciliter of blood. The symptoms of low testosterone include low sex drive, erectile dysfunction, mood problems, fatigue, and sleep disturbances. Of all men with below-normal testosterone levels, about one-half to two-thirds report symptoms.

Unlike a woman’s menopause, when estrogen levels plummet over months to very low levels, men’s “andropause” is a gradual decline of testosterone levels over years. The effects of low testosterone can be insidious, even go unnoticed.

Some men with low testosterone levels have symptoms without recognizing them, Herbst says. “They may still have a sex drive, but not realize how much it’s declined,” she says.

Men with symptoms of low testosterone can have significant impairment in quality of life. Current medical thinking is “these men should be treated with testosterone replacement,” Herbst says.

Low testosterone can be replaced by using a daily skin gel, patches worn on the skin, orally disintegrating tablets, or injections. The general recommendations are to raise the blood testosterone level only into the normal range.

Health Effects of Low Testosterone

Surprisingly little is known about the long-term health effects of low testosterone. Low testosterone is associated with several chronic medical conditions, including obesity, diabetes, depression, and possibly cardiovascular disease. However, “It’s not clear at all that [low testosterone] causes these conditions,” Herbst says. “In fact, it might be the other way around.”

The same processes that lead to medical illness -- causing diabetes and high blood pressure, for example -- could potentially also be causes of low testosterone, says Andre Araujo, PhD, an epidemiologist and researcher on testosterone deficiency. “It’s possible that low testosterone levels serve as a marker of health decline in general,” he says.

Testosterone builds bone, and low testosterone can lead to thinning of the bones, called osteoporosis. Men with hip fractures tend to have low testosterone. As yet, there is no proof that testosterone therapy reduces fracture risk. Still, most physicians would treat a man with low bone density with testosterone, Herbst says.

 

Testosterone Replacement: Benefits and Risks

Prescriptions for testosterone replacement have risen more than 17 fold in recent years. Some experts applaud the increase, while others sound a note of caution. Testosterone replacement in available doses is felt to be generally safe, but “we just don’t know the long-term benefits or the risks yet,” Herbst says.

Some evidence suggests that many men with symptomatic low testosterone don’t get treated, Araujo says. He and his colleagues found relatively low treatment rates in Boston, in a recent study.

“Only about 12 percent of men with symptomatic androgen deficiency were being treated,” Araujo says. “Without access to the medical data, we can’t say they should have been. But we can say that it didn’t seem to be due to poor access to care or unwillingness on their part.”

Men have a wide variation in response to testosterone replacement. “I wish all guys behaved the same when you give them testosterone,” Herbst says. “They don’t.”

In her specialty clinic, “about 10% of men don’t get much of a response. About 90% see some sort of improvement, and about one in 10 of them are ecstatic,” Herbst says. In clinical studies, the majority of men with low testosterone have improved erectile dysfunction and sex drive with testosterone replacement. The degree of response varies widely, though, and the long-term response isn’t known.

According to the Endocrine Society’s clinical guidelines, certain men shouldn’t take testosterone supplements. Men with metastatic prostate cancer or breast cancer absolutely shouldn’t, because testosterone can stimulate these cancers to grow. Other conditions can potentially be made worse by testosterone therapy, including sleep apnea, severe benign prostatic hypertrophy, severe congestive heart failure, or high red blood cell counts (erythrocytosis).

Testosterone Replacement: Benefits and Risks continued...

Clinical trials to evaluate the benefits of testosterone replacement are underway. Until then, men with low testosterone symptoms whose blood tests show low testosterone levels will need to make their own decisions with their doctors.

That’s if those men can get themselves to speak up about symptoms of low testosterone, though. Herbst says most men in her clinic don’t ask about it. “It would be great if they would,” she says.