Does testosterone therapy help erectile dysfunction?

Testosterone therapy helps erectile dysfunction in a minority of men, and only when testosterone is genuinely low. Among men with hypogonadism, meaning low testosterone confirmed by blood testing alongside symptoms, reported success rates run to 35 to 40% [7]. Most men treated this way are not helped.

Low testosterone and erectile dysfunction overlap, but one rarely explains the other. Only about 10 to 20% of men seen for erectile dysfunction have any hormonal abnormality at all, and the usual cause is vascular, a problem with the blood supply rather than with hormones [6]. Estimates of how many men with erectile dysfunction have outright testosterone deficiency range from 1.7% to 35%, depending on who was studied and where the cut-off was drawn [4].

The trial evidence is mixed. A 2022 review of the randomised trials, studies that allocate men by chance to testosterone or to a dummy treatment containing no active drug, found the results conflicting and the positive findings frequently too small to be clinically meaningful [1]. Older reviews of men who had both low testosterone and erectile dysfunction reported the same inconsistency [11].

Testosterone on its own is not where the evidence looks best. One multicentre trial recruited men who had erectile dysfunction for at least three months, a testosterone reading below 400 nanograms per decilitre, the unit laboratories print testosterone in, and no useful response to sildenafil, the drug sold as Viagra [3]. Over 12 weeks, men given testosterone gel on top of sildenafil improved more on a standard erectile function questionnaire than men given a dummy gel plus sildenafil, and they reported better orgasm and more satisfaction [2]. Taking testosterone and Viagra together is the combination reviewers have been most willing to call convincing [11].

Guidelines from the European Academy of Andrology, the professional body for male reproductive medicine, published in 2020, land in the same place: testosterone can reliably improve overall sexual function in the short term in men with confirmed low testosterone, while the longer-term benefits stay uncertain and contested [15].

An erection is a blood flow event, and a chemical signal controls it. Nerves and the cells lining blood vessels release nitric oxide, a short-lived gas that tells the muscle in artery walls to relax so blood can fill the penis [2]. An enzyme called phosphodiesterase type 5 then breaks that signal down and ends the erection, and sildenafil works by blocking the enzyme [6].

Testosterone sits upstream of all of it. In animals, removing the testicles cuts the amount of nitric-oxide-making enzyme in erectile tissue, destroys smooth muscle, and leaves the penis unable to trap blood; replacing the testosterone reverses those changes [2][3]. That is the strongest part of the case, and it comes from animals rather than from men.

In men, treatment seems to work partly by repairing the lining of the blood vessels. Testosterone increased the production of nitric oxide by vessel-lining and nerve cells, and raised the number of circulating cells that patch up damaged vessel walls [8]. It also appears to be a precondition for sildenafil working at all: men with low testosterone did not respond to sildenafil until their testosterone was restored [8], which is why a minimum blood level is thought necessary for that class of drug to do its job [7].

Desire and erection do not move together. Testosterone raises sexual interest and the frequency of erections during sleep, while erections triggered by fantasy or by what a man sees change little [11].

Most of what is above comes from review articles rather than from large new trials, and the reviews themselves report no agreement on how low testosterone has to be before treatment is worth trying, when to combine it with another drug, or how long to continue [1].

The combination trial is narrower than it first looks. It recruited only men below 400 nanograms per decilitre who had already failed sildenafil, and it ran for 12 weeks [2][3]. It says nothing about men whose testosterone is normal, men who have never tried sildenafil, or what happens after three months.

The evidence does not apply to several groups:

• Men with normal testosterone. Erectile dysfunction can be driven by a different hormone entirely: raised prolactin, a hormone from the pituitary gland, went with worse erections in men with pituitary tumours whose testosterone was normal, and a drug that lowered prolactin restored function without changing testosterone [10]. That work is mostly in rats, supported by the clinical correlation.
• Men whose low testosterone comes from sickle cell disease, which affects up to 25% of them and damages the testicles by its own route [12].
• Men whose low testosterone follows past anabolic steroid use, which is managed differently and where an attempted pooled analysis found no study of adequate quality to include [14].
• Women. None of these papers measured anything in women.

The drug carries its own restrictions. It must not be used in men with untreated prostate or breast cancer, or in severe heart failure, and the same panel treats severe urinary symptoms and a red-cell share of blood above 48 to 50% as reasons for caution [15]. The prostate depends on androgens, so treatment can worsen urinary symptoms, and a prostate cancer that is present but not yet causing symptoms is a recognised concern [11].

Hormone optimisation is one of the services tracked in the Longevinsights clinic directory, and difficulty with erections is one of the complaints that brings men to those clinics. What a first visit should involve is set by the diagnosis rather than by the treatment: symptoms, plus repeatedly low morning testosterone measured fasting on a well-validated laboratory test, plus the exclusion of other causes of low testosterone before anything is prescribed [15].

For a man who is overweight, the guidelines put weight loss and other lifestyle change first, along with a review of any medicine that might be suppressing his own testosterone production [15]. Men over 40 are meant to have a prostate-specific antigen blood test, a marker measured in blood that can be raised in prostate cancer, and a physical examination of the prostate before treatment starts [15]. Testosterone absorbed through the skin is the recommended form for starting treatment, with injections and other routes also in use [13][15].

The second blood test is the step that separates the men this evidence applies to from the men it does not.