This interview with Abraham Morgentaler, M.D., originally appeared in Harvard Health in 2007. It is still relevant today.

It could be said that testosterone is what makes men, men. It gives them their characteristic deep voices, large muscles, and facial and body hair, distinguishing them from women. It stimulates the growth of the genitals at puberty, plays a role in sperm production, fuels libido, and contributes to normal erections. It also fosters the production of red blood cells, boosts mood, and aids cognition.

Over time, the testicular “machinery” that makes testosterone gradually becomes less effective, and testosterone levels start to fall, by about 1% a year, beginning in the 40s. As men get into their 50s, 60s, and beyond, they may start to have signs and symptoms of low testosterone such as lower sex drive and sense of vitality, erectile dysfunction, decreased energy, reduced muscle mass and bone density, and anemia. Researchers estimate that the condition affects anywhere from two to six million men in the United States. Yet it is an underdiagnosed problem, with only about 5% of those affected receiving treatment.

Studies have shown that testosterone-replacement therapy may offer a wide range of benefits for men, including improved libido, mood, cognition, muscle mass, bone density, and red blood cell production. But little consensus exists on what constitutes low testosterone, when testosterone supplementation makes sense, or what risks patients face. Much of the current debate focuses on the long-held belief that testosterone may stimulate prostate cancer.

Dr. Abraham Morgentaler, an associate professor of surgery at Harvard Medical School, the director of Men’s Health Boston, and a member of Perspectives’ editorial board, specializes in treating prostate diseases and male sexual and reproductive difficulties. He has developed particular expertise in treating low testosterone levels. In this interview, Dr. Morgentaler shares his views on current controversies, the treatment strategies he uses with his own patients, and why he thinks experts should reconsider the possible link between testosterone-replacement therapy and prostate cancer.

Symptoms and diagnosis

What signs and symptoms of low testosterone prompt the average man to see a doctor?

As a urologist, I tend to see men because they have sexual complaints. The primary hallmark of low testosterone is low sexual desire or libido, but another can be erectile dysfunction, and any man who complains of erectile dysfunction should get his testosterone level checked. Men may experience other symptoms, such as more difficulty achieving an orgasm, less-intense orgasms, a smaller amount of fluid from ejaculation, and a feeling of numbness in the penis when they see or experience something that would normally be arousing.

The more of these symptoms there are, the more likely it is that a man has low testosterone. Many physicians tend to dismiss these “soft symptoms” as a normal part of aging, but they are often treatable and reversible by normalizing testosterone levels.

Aren’t those the same symptoms that men have when they’re treated for benign prostatic hyperplasia, or BPH?

Not exactly. There are a number of drugs that may lessen sex drive, including the BPH drugs finasteride (Proscar) and dutasteride (Avodart). Those drugs can also decrease the amount of the ejaculatory fluid, no question. But a reduction in orgasm intensity usually does not go along with treatment for BPH. Erectile dysfunction does not usually go along with it either, though certainly if somebody has less sex drive or less interest, it’s more of a challenge to get a good erection.

How do you determine whether a man is a candidate for testosterone-replacement therapy?

There are two ways that we determine whether somebody has low testosterone. One is a blood test and the other is by characteristic symptoms and signs, and the correlation between those two methods is far from perfect. Generally men with the lowest testosterone have the most symptoms and men with highest testosterone have the least. But there are some men who have low levels of testosterone in their blood and have no symptoms.

Looking purely at the biochemical numbers, The Endocrine Society* considers low testosterone to be a total testosterone level of less than 300 ng/dl, and I think that’s a reasonable guide. But no one quite agrees on a number. It’s not like diabetes, where if your fasting glucose is above a certain level, they’ll say, “Okay, you’ve got it.” With testosterone, that break point is not quite as clear.

*Harvard Editor’s note: The Endocrine Society publishes clinical practice guidelines with recommendations for who should and shouldn’t receive testosterone therapy. See “Endocrine Society recommendations summarized.” For a complete copy of the guidelines, log on to www.endo-society.org.

Is total testosterone the right thing to be measuring? Or should we be measuring something else?

Well, this is another area of confusion and great debate, but I don’t think it’s as confusing as it appears to be in the literature. When most doctors learned about testosterone in medical school, they learned about total testosterone, or all the testosterone in the body. But about half of the testosterone that’s circulating in the bloodstream is not available to the cells. It’s tightly bound to a carrier molecule called sex hormone””binding globulin, which we abbreviate as SHBG.

The biologically available part of total testosterone is called free testosterone, and it’s readily available to the cells. Almost every lab has a blood test to measure free testosterone. Even though it’s only a small fraction of the total, the free testosterone level is a pretty good indicator of low testosterone. It’s not perfect, but the correlation is greater than with total testosterone.

This professional organization recommends testosterone therapy for men who have both

• low levels of testosterone in the blood (less than 300 ng/dl)
• symptoms of low testosterone.

Therapy is not recommended for men who have

• prostate or breast cancer
• a nodule on the prostate that can be felt during a DRE
• a PSA greater than 3 ng/ml without further evaluation
• a hematocrit greater than 50% or thick, viscous blood
• untreated obstructive sleep apnea
• severe lower urinary tract symptoms
• class III or IV heart failure.

Do time of day, diet, or other factors affect testosterone levels?

For years, the recommendation has been to get a testosterone value early in the morning because levels start to drop after 10 or 11 a.m. But the data behind that recommendation were drawn from healthy young men. Two recent studies showed little change in blood testosterone levels in men 40 and older over the course of the day. One reported no change in average testosterone until after 2 p.m. Between 2 and 6 p.m., it went down by 13%, a modest amount, and probably not enough to influence diagnosis. Most guidelines still say it’s important to do the test in the morning, but for men 40 and above, it probably doesn’t matter much, as long as they get their blood drawn before 5 or 6 p.m.

There are some very interesting findings about diet. For example, it appears that individuals who have a diet low in protein have lower testosterone levels than men who consume more protein. But diet hasn’t been studied thoroughly enough to make any clear recommendations.

Formulations

What forms of testosterone-replacement therapy are available?*

The oldest form is an injection, which we still use because it’s inexpensive and because we reliably get good testosterone levels in nearly everybody. The disadvantage is that a man needs to come in every few weeks to get a shot. A roller-coaster effect can also occur as blood testosterone levels peak and then return to baseline.

Topical therapies help maintain a more uniform level of blood testosterone. The first form of topical therapy was a patch, but it has a very high rate of skin irritation. In one study, as many as 40% of men who used the patch developed a red area on their skin. That limits its use.

The most commonly used testosterone preparation in the United States “” and the one I start almost everyone off with is a topical gel. You rub it on your shoulders or upper arms once a day. Based on my experience, it tends to be absorbed to good levels in about 80% to 85% of men, but that leaves a substantial number who don’t absorb enough for it to have a positive effect.

Other than improvement in sexual symptoms, what are some of the potential benefits of testosterone-replacement therapy?

Some studies have looked at testosterone therapy and cognition. Although the findings weren’t definitive, there was some evidence of cognitive improvement. Other studies have shown that it improves mood. Testosterone therapy has also been shown to be effective in the treatment of osteoporosis and in increasing muscle bulk and strength.*

Risks and precautions

What risks do you consider when prescribing testosterone-replacement therapy?

When patients ask about risks, I remind them that they already have testosterone in their system and that the goal of testosterone treatment is to restore its concentration back to what it was 10 or 15 years previously.

For example, testosterone can increase the hematocrit, the percentage of red blood cells in the bloodstream. If the hematocrit goes up too high, we worry about the blood becoming too viscous or thick, possibly predisposing someone to stroke or clotting events. Although, frankly, in a review that I wrote in the New England Journal of Medicine* where we reviewed as much of this as we could, we found no cases of stroke or severe clotting related to testosterone therapy. Nevertheless, the risk exists, so we want to be careful about giving testosterone to men who already have a high hematocrit, such as those with chronic obstructive pulmonary disease, or those who have a red-blood-cell disorder.

Although it’s rare to see swelling caused by fluid retention, physicians need to be careful when prescribing testosterone to men with compromised kidney or liver function, or some degree of congestive heart failure. It can also increase the oiliness of the skin, so that some men get acne or pimples, but that’s quite uncommon, as are sleep apnea and gynecomastia (breast enlargement).

What about the risk of developing prostate cancer?

I think that the biggest hurdle for most physicians prescribing testosterone is the fear that they’re going to promote prostate cancer.* That’s because more than six decades ago, it was shown that if you lowered testosterone in men whose prostate cancer had metastasized, their condition improved. (It became a standard therapy that we still use today for men with advanced prostate cancer. We call it androgen deprivation or androgen-suppressive therapy.) The thinking became that if lowering testosterone makes prostate cancer disappear, at least for a while, then raising it must make prostate cancer grow. But even though it’s been a widely held belief for six decades, no one has found any additional evidence to support the theory.

Haven’t there been any studies that follow men who go on testosterone-replacement therapy to see what their rate of cancer is compared with that in men who are not on it?

As with a number of treatments or medicines that have been around for a long, long time, it hasn’t been scrutinized like a new drug would be. And although they’ve been discussed, there aren’t any large-scale, randomized controlled clinical trials of testosterone-replacement therapy under way.*

There have been a number of smaller studies on men receiving testosterone-replacement therapy, and if you look at the results cumulatively, the rate of prostate cancer in these men was about 1% per year. If you look at men who show up for prostate cancer screening, same sort of age population, the rate tends to be about the same. You have to be cautious in comparing studies and combining the results, but there’s no signal in these results that testosterone-replacement therapy creates an unexpectedly high rate of prostate cancer.

We also have epidemiologic studies, like the Physicians’ Health Study, the Baltimore Longitudinal Study of Aging, and the Massachusetts Male Aging Study, that include tens of thousands of men who are followed for 5, 10, 15, or even 20 years. At the end of the study period, the researchers see who developed prostate cancer and who didn’t. They can then look at blood samples taken at the start of the study to see if, for example, the group that got prostate cancer had a higher level of testosterone over all. About 500,000 men have been entered in some 20 trials of this type around the world. Not one of those studies has shown a definitive correlation between prostate cancer and total testosterone. Three or four have shown weak associations, but none of those have been confirmed in subsequent studies.

Another point I’d like to make for people worried about a link between high testosterone and prostate cancer is that it just doesn’t make sense. Prostate cancer becomes more prevalent in men as they age, and that’s also when their testosterone levels decline. We almost never see it in men in their peak testosterone years, in their 20s for instance. We know from autopsy studies that 8% of men in their 20s already have tiny prostate cancers, so if testosterone really made prostate cancer grow so rapidly “” we used to talk about it like it was pouring gasoline on a fire “” we should see some appreciable rate of prostate cancer in men in their 20s. We don’t. So, I’m no longer worried that giving testosterone to men will make their hidden cancer grow, because I’m convinced that it doesn’t happen.

Can testosterone worsen BPH?

The evidence shows that testosterone treatment does not change the strength or rate of urine flow, does not change the ability to empty the bladder, and does not change other symptoms such as frequency or urgency of urination, as assessed by the American Urological Association Symptom Score or the International Prostate Symptom Score. I’ve had a couple of patients over the years who had some worsening of urinary symptoms with testosterone, but that’s rare, even with long-term use.

For the entire article and studies, go to https://agemed.org/e-journal/feature-article-november-2018-a-harvard-expert-shares-his-thoughts-on-testosterone-replacement-therapy/