Testosterone Supplements: Hype, but No Erection Benefits

You probably know that the male sex hormone, testosterone, plays a pivotal role in men’s sexuality. Consequently, when men develop erectile dysfunction (ED), many assume the cause is testosterone deficiency. They believe supplementation offers a quick fix, and many doctors are willing to prescribe it.

However, a large recent study (Macdowall 2022) shows that testosterone supplementation provides no erection boost. The hormone plays a clear role in sexual desire and frequency of self-sexing, but has no impact on sexual function, particularly on erections.

The Study

British researchers began with data from a huge survey of residents of England and Scotland (the Natsal-3 study) that, among other things, explored sexual attitudes and function. They asked 1,599 male Natsal-3 participants, aged 18 to 74, to provide morning saliva samples. The researchers analyzed the saliva for testosterone markers.

It’s unusual for researchers to use salivary testosterone. Most take blood samples. But the hormone can also be detected in saliva, which is much easier and cheaper to collect.

Blood and salivary levels of testosterone vary with age, health, weight, relationship status, the season of the year, and the time of day. The researchers used standard statistical techniques to minimize the impact of these confounders.

The researchers then correlated salivary testosterone with participants’ responses to the Natsal-3 sexuality questions. Corroborating many other studies, they found that testosterone impacts libido/desire, but not sexual function. Compared with men who had the lowest levels of testosterone, those with the highest reported somewhat more sex—not a great deal more, but some—more self-sexing, more vaginal intercourse, and more concurrent relationships. But the researchers found “no association between male sex hormone levels and sexual function.”

In other words, for most men, extra testosterone provokes desire but does not aid performance.

Things are different for the estimated 7 percent of men who have true testosterone deficiency. With a clinical deficiency, libido and erections collapse, and supplementation restores sexual desire and function. But we’re talking about just 7 percent of men, a small fraction. For men whose testosterone levels are in the normal range, or even on the low side of normal—now called “low T”—the most likely outcome of testosterone supplementation is increased sexual frustration. They want more sex and go after it. But their erection function remains unchanged.

Testosterone Supplementation Is Increasing

The recent study is by no means the only report showing that testosterone governs libido but not sexual function. Many studies corroborate this. As a result, you’d think doctors would prescribe supplementation to only the 7 percent of men suffering from a true deficiency. But since 2000, the number of American men taking the hormone has quadrupled to more than 2 million.

After around 40, male testosterone levels decrease slowly but steadily. This parallels menopausal estrogen decline in women. Many older men’s levels fall into the low-normal range, but low-T does not signal true deficiency, just age-related biological changes that are normal. Unfortunately, these days, a substantial number of doctors have stopped distinguishing between age-related testosterone decline and clinical deficiency. They advocate testosterone supplementation, calling the hormone a fountain of youth that restores older men’s flagging libidos and erections, and returns them to lean, muscled, youthful vigor.

In the early 2000s, as prescriptions for supplemental testosterone soared, the Food and Drug Administration (FDA) became concerned. Some evidence suggests that excessively high levels of testosterone may increase the risk of cardiovascular disease. The hormone thickens the blood, a significant risk factor for heart disease and most strokes. In addition, testosterone accelerates atherosclerosis, the arterial narrowing at the root of both of these conditions. Excessive testosterone is also associated with an increased risk of prostate cancer—as common and deadly in men as breast cancer in women. During the late-twentieth century, concerns about the hormone’s potentially serious downsides limited prescriptions.

But starting around the millennium, some prominent researchers argued that testosterone does not increase the risk of cardiovascular disease and prostate cancer, at least in studies lasting only a few years. As a result, increasing numbers of physicians have been prescribing it to more and more middle-aged men complaining of fatigue, libido decline, and erection problems.

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Testosterone and Politics

In 2014, the FDA convened an expert panel to assess the pros and cons of testosterone supplementation. The experts overwhelmingly urged the agency—by a vote of 19 to 1—to impose strict limits on prescribing it. Their arguments:

• Prescriptions had spiked upward, but no evidence suggested any jump in true deficiency.
• In men who are actually deficient, supplementation restores libido and erection function. But in low-T men—who are still in the normal range—extra testosterone has only a modest impact on libido and none on erection function.
• Audits have shown that many physicians have written prescriptions without blood tests sufficient to establish men’s true levels.
• As a result, many men taking testosterone don’t need it, which subjects them to unnecessary expense and side effects, and potentially serious health hazards.
• Testosterone deficiency is most likely in men over 65. Yet currently, younger men account for most prescriptions.
• Testosterone supplementation is associated with depression and intentional self-harm. That’s what University of Miami researchers discovered in a study of 263,579 men who took testosterone and more than 17 million who did not. The hormone use was independently associated with both major depression (P < .0001) and suicide attempts (P < .0001).
• Finally, the debate over testosterone replacement bears an eerie similarity to the controversy decades ago surrounding estrogen hormone replacement therapy (HRT) in older women—also initially proclaimed to restore youthfulness, then later shown to increase the risk of heart disease and breast cancer.

Who Should Take Testosterone

The Endocrine Society recommends testosterone supplementation only for men with unequivocal deficiency, a finding that requires several blood tests at different times of the day because testosterone levels fluctuate with the time of day. Men who appear low in one test often look normal in others. Meanwhile, researchers at the University of Texas (UT) Medical Branch in Galveston have found that 25 percent of the men taking testosterone had just one blood test prior to receiving prescriptions, suggesting that many doctors have prescribed it irresponsibly. Even if multiple blood tests show a clear deficiency, the Endocrine Society recommends against supplementation unless men report libido collapse.

No credible evidence indicates any recent increase in true testosterone deficiency. The quadrupling of prescriptions since 2000 suggests the hormone is over-prescribed. Hence the FDA panel’s near-unanimous recommendation that the agency move to reduce prescribing.

If you have received a prescription without libido collapse and multiple blood tests, you may be taking the hormone unnecessarily. And if breathless claims about libido enhancement, firmer erections, and improved vitality have you considering supplementation, I hope the FDA panel’s 19-to-1 vote against supplementation encourages you to reconsider.