The Scary Side Effects of Testosterone Replacement Therapy

Anna Medaris Miller

Too good to be true?

A jacked physique. Gossip-worthy bedroom abilities. Boundless energy. Happiness! With promises of results like these, it's no wonder men seek testosterone replacement therapy like kids fish for candy. "They've all got this notion that it's going to make them into this bodybuilder or Casanova," says Dr. Ajay Nangia, a urologist at the University of Kansas Health System. But while some medical conditions warrant the therapy -- a synthetic form of testosterone that men can take as a gel, injection, patch or implant -- general symptoms of aging like lagging libido, sagging skin and dragging energy, which the drugs are loudly marketed for, often don't.

Murky criteria

Testosterone replacement therapy is approved by the U.S. Food and Drug Administration to treat low testosterone, aka "low T," which can be directly linked to some medical conditions like undescended testicles or treatments like chemotherapy. But only 11 percent of prescriptions go to these types of patients, says Dr. Mohit Khera, an associate professor of urology at Baylor College of Medicine. Other men can acquire it if (imperfect) blood tests show low levels of testosterone and they have ubiquitous symptoms like fatigue or erectile dysfunction. "All of that makes it murky for those who have real problems," Nangia says. Here's how, in some cases, testosterone replacement therapy may do more harm than good:

1. Infertility

More than simply busying pharmacists for potentially unnecessary prescriptions, men who take testosterone supplements without a clear medical indication often unknowingly set themselves up for serious risks, namely infertility, says Dr. Serena H. Chen, medical and scientific advisor at Progyny, a fertility solutions company, and a reproductive endocrinologist at IRMS in Livingston, New Jersey. That's because your brain stops telling your body to produce testosterone when it senses there's enough. Over time, that can lead to testicular cell damage, cell death and even visible testicle shrinkage, Chen says, which inhibits sperm production. "Then [patients] come to me and say, 'No one told me that I could become infertile when I started,' and that's a problem," Khera says.

2. Heart problems

If you read the prescription label or listen to the risks recited on commercials to combat low T, you'll see or hear that some research has linked testosterone therapy with an increased risk for cardiovascular conditions including blood clots, heart attacks and strokes. In fact, one study just published in the Journal of the American Medical Association found that older men taking testosterone had an increased risk of developing plaque buildup in the arteries of their hearts over the course of a year compared to men not on the therapy. While stronger research has shown no link between heart problems and testosterone replacement therapy, Nangia says, the FDA has deemed the risk worth mentioning.

3. Effects on the prostate

For decades, many urologists believed testosterone replacement therapy could lead to prostate cancer, but fortunately, that link has been mostly debunked and even reversed, Khera says. "The pendulum is shifting," he says. Still, it appears the therapy can have some negative effect on the prostate in men who already have some conditions, including prostate cancer and benign prostatic hypertrophy, or an enlarged prostate, which causes the need for frequent urination. That's why it's critical for men to receive appropriate screenings before receiving and while on treatment. As opposed to up-to-date primary care doctors and urologists, "testosterone clinics or or people who aren't as men's health-oriented are feeding into an insecurity," Nangia says.

4. Mood issues

Men looking to boost their bodybuilding efforts by turning to high doses of testosterone supplements sold on the black market -- where such hormones are often formulated to suit horses, not humans -- are playing with fire, Khera says. "When testosterone levels are too high, there's a phenomenon such as 'roid rage' where they get angry," he says. When dosed appropriately, on the other hand, patients may find some relief from depressive symptoms, which have been linked to low testosterone. "You have to realize you don't want to be too low or too high," Khera says.

5. 'Infecting' others

Applying a gel daily, which many men on testosterone replacement therapy do, comes with risks, including skin irritation, hypertension due to sodium retention and even the chance of accidentally transferring some of the gel to others, Khera says. If the gel rubs off on your child, for example, he or she may develop signs of early puberty; if it smears onto a woman's skin, she could experience changes in body hair or acne, according to one of the gel's websites. "If you're managed appropriately, it can be easy" to account for these and other risks, says Khera, who recommends working with your primary care doctor or, when necessary, a urologist.

6. Missed opportunities

Testosterone replacement therapy does have some merit -- it's "very effective" for sexual symptoms like erectile dysfunction, Khera says, and has been shown to improve muscle mass, bone density and insulin sensitivity in some men. But treating ubiquitous symptoms of aging with testosterone often causes men to miss the opportunity to pursue healthier, more effective, long-term solutions such as losing weight, drinking less alcohol or addressing an underlying condition like thyroid problems. "I think with more research and bigger studies, you're going to see some benefits with hormone replacement therapy," Nangia says. "But the question is: How much, and is it sustainable and will it make health better down the road without risk?"