The use of testosterone is rising rapidly among Swedish men, and online the hormone is often sold as an elixir of masculinity. But the myths are misleading and unnecessary treatment is not without risk.
Text: Anders Nilsson, först publicerad i tidningen Medicinsk Vetenskap nr 1 20256.
"There is a lot of testosterone in the room," explained a rhetoric expert when Aftonbladet asked her to analyse the tense meeting between Presidents Trump and Zelensky at the White House in spring 2025. Her comment reflects a widespread belief that testosterone is linked to a stereotypical form of masculinity - energetic, aggressive, dominant, perhaps even violent. The Swedish term testosteronstinn ("testosterone-fuelled") is used so frequently that it has earned its own entry in the official dictionary of the Swedish Academy. In Swedish media it has appeared thousands of times to describe anything perceived as excessively masculine, from rock music to international politics.
In various forms of overt or subtle marketing, we encounter a similar connection between testosterone and masculinity, although presented positively. High testosterone levels are depicted as the key to all the qualities a "proper man" is expected to aspire to: strength, libido, confidence and drive. Influential men who cultivate a macho image, like Donald Trump and Andrew Tate, have spoken openly about their supposedly high testosterone levels.
But the myths surrounding this male sex hormone have a weak connection to reality, explains Stefan Arver , associate professor of endocrinology, the study of hormones, at Karolinska Institutet. Testosterone is undeniably an important hormone, and those who genuinely suffer from a deficiency should receive supplements. But most men have perfectly adequate testosterone levels and gain nothing by trying to boost them further, he emphasises.
Increased prescription of testosterone
In Sweden, testosterone is a prescription-only drug. In 2006, it was prescribed to around 8,000 men. By 2024, the number had risen to just over 26,000. Stefan Arver does not believe this increase is due to healthcare suddenly becoming better at detecting and treating men with testosterone deficiency.
"Much of the increase is probably going to the wrong people. A lot of men experience symptoms like fatigue or reduced libido, and when they hear testosterone described in advertising, they think, 'What harm could it do to try?' But these symptoms are usually due to other causes, and unnecessary testosterone treatment is not risk-free. You fall into a trap," says Stefan Arver.
The first thing that happens when testosterone is added from outside is that the body compensates by shutting down its own production. The testicles shrink, and levels drop again.
"So, you might raise the dose, and that is when the side effects begin. Testosterone affects the entire body. For example, it increases the production of red blood cells, which makes the blood thicker and can cause symptoms like headaches and itching. The heart has to work harder and, in the worst case, the risk of blood clots may increase," he says.
Testosterone is a versatile hormone. It is essential for the survival of species because it drives the development of male sex characteristics in the male foetuses and sexual desire and capacity in adults. Another important role is its anabolic or building effect. It is involved whenever the body creates new cells and tissues, muscles, bones, connective tissue, skin and red blood cells. This is why it is classed as an anabolic steroid.
"Anabolic literally means 'building up'. Testosterone, together with insulin and growth hormone, is one of our most important anabolic hormones," says Stefan Arver.
A third aspect is testosterone's link to body hair. It stimulates hair growth on the face and body but has the opposite effect on the scalp.
Testosterone is also linked to our sense of wellbeing.
"It has a positive effect on mood and on how we perceive ourselves - whether we feel we are good enough. Testosterone deficiency increases the risk of depression. Not the heaviest, most severe forms, but you lose zest for life and the sense of enjoyment," says Stefan Arver.
The connection is well documented, but the underlying mechanisms are still unknown.
"Much points to a link to the brain's reward system, for example dopamine levels, but we do not know for certain."
Testosterone deficiency is rare
Normal testosterone levels in men range between roughly 10 and 30 nanomoles per litre (nmol/L). Anyone with lower levels may be at risk of testosterone deficiency. It does occur, but rarely, and when it does, it is usually a sign that something else is wrong. If testosterone deficiency is suspected, an investigation is needed, stresses Stefan Arver. The underlying cause can be anything from a pituitary tumour to a chronic inflammatory disease or lifestyle factors.
"It comes down to the usual pitfalls in life: gaining weight, not being active enough, eating poorly and drinking too much alcohol. Obesity lowers testosterone while increasing oestrogen," he says.
The body's testosterone production declines only marginally with age. Men do not develop testosterone deficiency simply because they grow older, he emphasises.
"You will see claims that all men over 40 should take testosterone, or that there's a male equivalent of the menopause that causes testosterone deficiency. That is simply not true. There is no such thing as a male menopause."
Measuring testosterone levels is easy, but interpreting the results requires expertise. The test measures total testosterone in the body, but only a small fraction of it is biologically active. Most of it is tightly bound to a protein, making it unavailable, and this proportion varies widely between individuals.
"This means that someone with 10 nmol/L might actually have more available testosterone than someone at 30 nmol/L," says Stefan Arver.
Another reason not to worry about values at the lower end of the normal range is that, in most cases, adding more testosterone does not amplify the effect, he points out.
"If you do not have a genuine deficiency, taking extra testosterone will not improve the things that men, in my experience, are usually looking for, like feeling more energetic, having more stamina or a stronger sex drive. You hit the ceiling; the system is saturated."
Stefan Arver works at Anova, the Centre for Andrology, Sexual Medicine and Trans Medicine, run jointly by Karolinska University Hospital and Karolinska Institutet. There, he conducts research with colleagues, including Jussi Jokinen , professor of psychiatry at Umeå University. Among other things, they have studied testosterone's role in male sexual function.
"Testosterone is essential for male sexuality. If you lose your testosterone, you lose all interest in sex and the ability to function sexually. When you get the testosterone back, your sexuality returns," says Jussi Jokinen.
As in other areas, extra testosterone only has an effect if it corrects a deficiency. Higher-than-adequate levels do not lead to increased libido or difficulty controlling sexual impulses.
"There is a myth that so-called sex addiction is linked to high testosterone levels, but that is not true. We have measured this ourselves in a recent study on men with compulsive sexual behaviour. There was no difference compared with other men."
Certain drugs used to treat hormone-sensitive cancers block testosterone production. Research at Karolinska Institutet has shown that these can also be used to treat paedophilic disorder and reduce the risk of future offences. The intervention is effective and can be used acutely. For long-term treatment, however, other options are preferable to inducing prolonged testosterone deficiency, explains Jokinen.
"We are currently running a study comparing cognitive behavioural therapy with drug treatment for men who are seeking help for a sexual interest in children," he says.
Testosterone also plays a role in women's sexuality. Prescriptions to women are far lower than for men but are rising rapidly, largely among women seeking to regain their sexual desire after the hormonal changes of menopause.
"This is not my research area, but I understand the treatment can give good results. I would also like to emphasise that sexuality in both men and women is very complex. A single hormone is just one of many factors involved," says Jokinen.
Testosterone's muscle-building properties have made it the dominant performance-enhancing substance. In fact, illegal use is far more common than legitimate medical use.
"The number of people who use performance-enhancing drugs in Sweden is estimated at between 50,000 and100,000, and in almost all cases it involves testosterone," says Mikael Lehtihet, associate professor of endocrinology, who researches testosterone and doping at the Department of Medicine, Huddinge, Karolinska Institutet.
People who use performance-enhancing substances come from all walks of life, he explains, and have only one thing in common: they enjoy strength training. The vast majority are men.
"Far fewer women use performance-enhancing substances, but they do exist. Often they are introduced to doping by a father or boyfriend," he says.
Risks with higher doses
When it comes to testosterone's muscle-building effect, higher doses genuinely do lead to greater results. But higher doses also mean more pronounced side effects: shrinking testicles, breast development in men, acne, increased body hair and hair loss on the scalp for both sexes, deepened voice and enlarged clitoris in women. Testosterone also affects blood pressure and blood formation, and thereby the cardiovascular system, kidneys and the risk of blood clots.
"The risks depend on how long someone uses performance-enhancing substances, their genetics and their overall lifestyle. People are affected very differently. I have patients who have used doping substances for 40 years and feel fine, but also those who have suffered heart attacks at a young age or ended up on dialysis," says Mikael Lehtihet.
A very common belief is that high testosterone makes people more aggressive. This is not true, he explains. Men who use testosterone for doping can certainly be aggressive. But if you exclude other factors that complicate the picture, such as other substance abuse and personality disorders, no such link can be demonstrated.
"In fact, it is the person with testosterone deficiency, hypogonadism, who is irritable and can become aggressive. Increasing testosterone in those cases can make them calmer and more balanced. But no matter how often you say it, people seem unwilling to let go of the idea that testosterone causes aggression."
Mikael Lehtihet is concerned about the rapid rise in testosterone prescriptions.
"We know that healthcare has missed many patients with genuine deficiency, but unfortunately, I think much of the increase is going to others."
A large proportion is being prescribed by private GPs to men in their 50s, with no underlying disease, he notes. This is not an age typically associated with deficiency, but a time in life when many men begin wishing they felt a bit younger, with more energy and desire.
"I think we are seeing both under-prescribing and over-prescribing at the same time. And it is not good at all when it is prescribed without medical justification."
Fact testosterone
Testosterone is a hormone belonging to the steroid group: fat-soluble substances derived from cholesterol. It is known as the male sex hormone but is also found in women, albeit at lower concentrations. Likewise, oestrogen, commonly called the female sex hormone, is also present in men.
Testosterone is produced in the testicles, adrenal glands and ovaries, and is carried by the bloodstream to various organs, such as muscles and the brain. It binds to specific receptors and influences cellular activity.
