results of large testosterone gel study

Final results of large testosterone supplementation study in men 

Endocrinology, Urology

Last year, we reported partial results of a large research study carried out by the National Institutes of Health (NIH-USA) regarding supplemental testosterone gel for older men. The NIH released partial results in 2016 and now just published the full results, which we will summarize here.

The purpose of the study was to see if older men, who took supplemental testosterone gel every day, would have improvements or suffer complications from the treatment after a year. The study included 790 men aged 65 or older, all of whom had low testosterone levels—below 275 ng/dl, as well as symptoms of low testosterone, such as lowered sex drive, or low energy.

The study was designed in the best possible way, meaning it was “double blind, controlled”. One half of the men were randomly assigned to receive the actual testosterone gel, and the other half received placebo gel. Neither the men nor the researchers knew who was who until the code was broken at the end of the study.

For the men receiving the real medication, the goal was to raise their testosterone levels to the average level of an man in his 20s or 30s. The NIH looked at 7 distinct results to see if the medication helped: physical performance, sexual functioning, energy level, thinking ability, bone density, atherosclerotic plaque formation in the heart, and anemia (which sometimes accompanies low testosterone).

Summary of results of testosterone supplementation

Physical performance and testosterone 

The men taking testosterone showed mild improvements in physical performance when measured by walking ability, but tests of strength (for example, weightlifting) were not part of the study.

Sexual functioning

The men taking testosterone noted “mild-to-moderate” improvements in sexual functioning. They had better desire, sexual activity, and erections (though the authors noted that men would get a better response for erections using drugs such as Viagra or Cialis—though these drugs do not help libido).

Energy level

The men on testosterone did feel that their energy level was better (thought that was hard to measure), and there was a “small but significant” improvement in their mood and any depression symptoms.

Thinking ability

Here there was no difference between the two groups. Testosterone does not appear to improve cognition.

Bone density

The men on testosterone did show improved bone density.

Atherosclerotic plaque formation in heart

Here is where there was some concern regarding the men on testosterone, since these men overall showed an increase in “soft” atherosclerotic plaques in the heart, measured by heart CT scans. There was no increase in heart attacks, but the researchers were concerned that over time, some of these men might have a greater risk of heart attacks. However, some other studies have suggested a lower risk of heart attacks in men on testosterone. This area is still unresolved, but the NIH study raised some “red flags”.


The men taking testosterone showed significant improvements if they had anemia.


The results showed mild to moderate improvements in a number of areas, but there was concern that perhaps, after longer term use of testosterone supplements, some men might be pre-disposing themselves to a greater risk of heart attacks. This is still controversial. The concern about greater risk of prostate cancer from testosterone supplementation has largely been rejected. If you are a man concerned about your testosterone levels, the best approach is to discuss the issues with your doctor, preferably an endocrinologist.

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Read also in ProcuraMed:

Study: Testosterone therapy doesn’t up cancer risk

Does testosterone gel really help middle-age men?

Esta postagem também está disponível em: Portuguese (Brazil)

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