The FDA warns that prescription testosterone is only approved for men who have low testosterone due to certain medical conditions.

Wladimir Bulgar /Getty Images/Science Photo Libra

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Wladimir Bulgar /Getty Images/Science Photo Libra

The FDA warns that prescription testosterone is only approved for men who have low testosterone due to certain medical conditions.

Wladimir Bulgar /Getty Images/Science Photo Libra

In 2014 Time magazine published a cover titled story Menopause?!, documenting the rise of the $2 billion testosterone industry, which marketed the hormone as a way to fend off age-related declines in sexual function, energy and strength.

As interest has increased, so have questions about security. A small studio showed that testosterone could improve muscle strength in older men, but it also found something unexpected: a higher rate of adverse cardiovascular events such as heart attacks. In 2015 the FDA required manufacturers to add Warning labels inform consumers about potential risks. The use of prescription testosterone has begun to decline.

Now a new study released on Friday could ease the minds of people interested in the treatment. It notes men who had low testosterone levels and received the prescription testosterone gel to raise the sex hormone level, he did not have a higher rate of heart attacks or strokes, compared with men who took a placebo.

« The results of this study provide reassuring and substantial evidence that testosterone replacement therapy does not appreciably increase the risk of death from cardiovascular causes when appropriately prescribed, » says the study author, Dr. Michael Lincoln of the Cleveland Clinic. The results are published in New England Journal of Medicine.

(This study did not evaluate testosterone-containing, over-the-counter nutritional supplements that are not regulated as drugs.)

The new study aims to better understand the effects of testosterone on cardiovascular risks, explains the study’s senior author Doctor Steven Nissen, a Cleveland Clinic cardiologist. However, he interprets the results with caution.

« Although the study showed some evidence that testosterone treatment may be safe for men with low testosterone levels, these findings should not be used as a justification for widespread prescribing, » says Nissen.

THE FDA says treatment it should be reserved for men with low testosterone levels confirmed by laboratory tests. Nissen says he is « concerned » that the results could be interpreted by bodybuilders and athletes looking to enhance performance as a green light to use testosterone. « I really think it’s a potential risk, » says Nissen.

Nissen points out that all participants had a pre-existing or elevated risk of cardiovascular disease symptoms of hypogonadism, a medical term for not producing enough testosterone. The study included about 5,200 men, ages 45 to 80, who were assigned to use a placebo gel or testosterone gel, which is rubbed into the skin, every day for 22 months.

Of the men who used testosterone gel, 7% had a major cardiac event, such as a heart attack or stroke. Of those who used the placebo, 7.3% had a major cardiac event. And, given that all participants were at high risk for heart problems, the findings suggest that testosterone doesn’t increase risk. As reassuring as that is, Nissen points to other safety issues found during the study, including an increased risk of heart arrhythmias in men taking testosterone.

« We didn’t expect that, » says Nissen. Additionally, there were small increases in the risk of renal injury and pulmonary embolism. The study authors conclude that the findings « support current guidelines that testosterone should be used with caution » in men who have had a previous blood clot event.

The study was funded by a group of testosterone manufacturers including AbbVie, creator of Androgel, what was the product used in the study. Common side effects and risks associated with the product are included in the marketing material, including a possible increased risk of prostate cancer. In the new study, prostate cancer occurred in 12 patients (0.5%) in the testosterone group compared with 11 patients (0.4%) in the placebo group. The study was independently managed by the Cleveland Clinic Coordinating Center for Clinical Research.

The results of the new study are « very encouraging, » says Dr. Kambiz Tajkarimi, a board-certified urologist in the Washington, DC area who treats people with sexual dysfunction. He prescribes testosterone, including pellets marketed as bioidentical HRT, to many of his patients, and says he uses them himself.

« I was so tired, » says Tajkarimi, who is in his early 50s. Now, he says he has more energy, which he attributes to the testosterone pellets. « I think this is a really beneficial treatment. »

However, clinical trials of testosterone indicate modest or even imperceptible symptom relief or benefits of testosterone replacement therapy. Dr. Steven Woloshin of the Dartmouth Institute for Health Policy & Clinical Practice, says one of the important findings of the new study is that about 60 percent of the men in the clinical trial stopped taking testosterone during the trial. Many said their symptoms persisted.

« This is just another way of saying it didn’t work or didn’t work enough to [men] to notice an advantage,” says Woloshin.

Previous searches, including a study published in 2016 showed that testosterone led to improvements in sexual function and mood among men 65 and older, but a close look at previous research shows very modest benefits, Woloshin says. For example, a 0.6-point improvement on a 13-point scale in sexual function and a 0.5-point improvement on a 45-point mood scale, « an effect many men are unlikely to notice, » he says. Woloshin. Also, there were no improvements in fatigue.

Big picture, Woloshin says, he too is concerned that the study findings could revive interest in testosterone replacement therapy, among people who may not benefit from it. « It’s not the fountain of youth, » says Woloshin. « You will feel the effects of aging. »

Nissen agrees. « Men want to feel like they did when they were young, » he says. But, of course, we can’t go back in time.