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. Taken together, these signs and symptoms are often called hypogonadism (“hypo” meaning low functioning and “gonadism” referring to the testicles). 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 with hypogonadism, 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 and the director of Men’s Health Boston, 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.
What changes do you see taking place on the testosterone front over the next five years?
I think that the importance of testosterone for cardiovascular health is going to be increasingly recognized. In the past, because men die of heart attacks more often than women and men have more testosterone, the fear has been that testosterone causes heart problems. But every single study of whether testosterone is bad for the heart has been negative, and what people haven’t pointed out in most of those negative studies is that there may be a beneficial effect.
I think we’ll also find out in five years that there very well may be general health benefits of having normal testosterone compared to low testosterone. There are growing data for all-cause mortality that men who have low testosterone die earlier than those who have normal testosterone. A study by the Veterans Administration reported about a year ago showed low testosterone levels were associated with a dramatically increased mortality rate. It’s hard to know why that is, but I think we’ll be focused on that in the coming years.
Any closing thoughts?
I think that low testosterone is under-recognized, its effects are greatly underappreciated, and its diagnosis isn’t readily understood. This is an area that has tremendous research potential in the coming years.*