Tired, listless, no sex drive: Is testosterone to blame?
Testosterone is one of the most talked-about hormones of our time: sometimes hailed as a “fountain of youth,” other times demonized as a performance-enhancing drug. Dr. Christoph Keining has been examining the evidence behind the hype for many years—and in this interview, he explains when a deficiency should truly be treated, why men are less likely to go for preventive checkups, and what this has to do with mental health. It boosts dopamine production. Dopamine is what makes you want to get things done.
"It used to be demonized as a performance-enhancing drug"
How did you come to specialize in the topic of testosterone
?
Dr. Christoph Keining: “Testosterone is quite a polarizing topic: On the one hand, it’s currently treated almost like a myth—social media is full of promises of a fountain of youth and anti-aging benefits. In the past, however, it was often demonized and branded as a performance-enhancing drug. As is so often the case, the truth lies somewhere in between: Testosterone is by no means a miracle pill, but rather a medication like any other, with effects and
side effects.”
"It's important to distinguish clearly who really benefits from this. My task was to delve into the evidence and see what the studies actually say. I'm also a systemic therapist and couples therapist, and hormonal factors are just one piece of the puzzle—they shouldn't be overemphasized, but they shouldn't be neglected either."
What does it actually mean to have too little or too much testosterone in your body?
Dr. Christoph Keining: “I’ll start with the shortcoming: In medicine, there’s a saying: ‘Don’t treat the lab, treat the patient.’ We don’t want to treat lab values; we want to treat symptoms. To me, a low lab value isn’t, on its own, an indication for treatment—it only makes sense if symptoms are present and match the value.”
The symptoms are often nonspecific: fatigue, exhaustion, loss of libido, depression, burnout—many differential diagnoses overlap. However, in recent years, high-quality studies have been published showing that an untreated deficiency significantly increases the risk of heart attack and stroke. Previously, the concern was the opposite. Today we know that for those with a deficiency, supplementation can even be beneficial as a preventive measure.
On the other hand, levels that are too high—that is, levels well above physiological norms—can really only be achieved through doping, using much higher doses than those used in medically indicated replacement therapy.
"In women, overproduction rarely occurs naturally; if it does, I would investigate the cause. An overdose, on the other hand, manifests as high blood pressure, fluid retention, breast growth in men, changes in liver function tests, or mood swings—which is why
close monitoring is crucial."
There is a debate over whether female menopause can be compared to a
male “andropause.”
Dr. Christoph Keining: “In certain respects, the two can be compared. There is such a thing as andropause, but not every man with low testosterone levels automatically experiences symptoms—whereas it is extremely rare for women to go through this phase of life completely symptom-free.”
But men can also experience similar symptoms: loss of libido, changes in body composition, increased visceral belly fat, lack of strength, brain fog, faster exhaustion, and irritability. And yes—this is a myth: Too much testosterone does not make you aggressive. The opposite is true: A deficiency makes you irritable and aggressive."
When should you consider getting tested for a deficiency
?
Dr. Christoph Keining: “At the very latest when you start to feel: ‘I don’t feel the same as I used to; something isn’t right.’ That’s when it’s worth looking at the differential diagnoses: What’s causing the fatigue, the lack of drive, and the loss of libido? The classic testosterone-related symptoms are libido, erection quality, and morning erections—but taken in isolation, that’s not yet
a cause for concern.
"It's only when several symptoms occur together that it makes sense to get tested. And here's something interesting: Even young patients in their early 30s can have a genuine deficiency—this is often underdiagnosed because people say, 'You're still young; that can't possibly be the case for you.'"
Why is it that younger men, in particular, are increasingly coming to see you at your practice
?
Dr. Christoph Keining: “It ’s definitely multifactorial. Processed foods, high stress levels, sedentary lifestyles, lack of exercise, and an increase in metabolic diseases like diabetes—all of these factors cause levels to drop. For people who lose weight, exercise, sleep better, and reduce stress, levels often rise again on their own, without any need for replacement therapy.”
"But: Even young people who lead a healthy lifestyle can have true hypogonadism (a hormonal deficiency in which the body does not produce enough of its own testosterone, which can lead to related symptoms). These cases need to be identified and treated."
What treatment options are available—and what sets your approach apart?
Dr. Christoph Keining: “Traditionally , in Germany there is a gel and a long-acting injection that is administered every few weeks. The problem with this is that it causes significant fluctuations in hormone levels. First, the level rises very high—almost to the point of doping—and then it drops again until the symptoms return. It’s like a roller coaster.”
Instead, I work with a testosterone ester—a form of testosterone in which the chemical bond to a so-called ester controls how quickly the active ingredient is released and broken down in the body.
Depending on the ester, this results in differences in half-life and duration of action—so there are short- and
long-acting forms of testosterone. The preparation I use is injected twice a week, which keeps my levels constant. In my experience, this allows me to achieve true freedom from symptoms, not just relief."
"You feel like getting things done again"
What are some persistent myths about testosterone?
Dr. Christoph Keining: “That it’s just a performance-enhancing drug for bodybuilders. Recent studies have clearly refuted the claim that it increases the risk of prostate cancer or heart attack. And: High testosterone levels don’t automatically lead to a good erection—that also depends on estrogen—but sufficient testosterone definitely boosts libido.”
"In my view, the main effect is actually psychological: it boosts dopamine production. Dopamine makes you want to get things done—the opposite of procrastination."
One major issue is that men are less likely to go for preventive checkups than
women. Why do you think that is?
Dr. Christoph Keining: “That ’s a good question, and I don’t have a simple answer. It might be an old stereotype: Women are integrated into the healthcare system early on through gynecology. Men often lack this basic understanding. And we also need to take a critical look at our profession: Are we doing a good enough job of reaching out to men? The classic scenario is: The man comes in because his partner sent him.”
Mental health plays a huge role here—the suicide rate among men is significantly higher, and I believe that’s partly because there isn’t enough connection and communication among men. That’s why I think initiatives like “Movember”*, where people in England even talk about preventive care in pubs
, make perfect sense—even if this is just the beginning
."
What are your hopes for the future—in research, but also
in society?
Dr. Christoph Keining: “From a purely medical perspective, I see exciting developments with GLP-1 agonists—
the so-called weight-loss injections—which can improve the overall risk profile
in cases of severe obesity, to the point where testosterone replacement therapy is sometimes no longer necessary. But what I’d really like to see is more men’s groups, more places—like soccer stadiums or pubs—where people can talk openly about health. This can make a huge difference in terms of prevention, simply because
it raises awareness.”
Thank you very much for the interview!
*Movember is an international campaign held in November in which men grow mustaches to raise awareness and funds for men’s health. The focus is on raising awareness about prostate and testicular cancer screening, mental health, and suicide prevention. The campaign deliberately relies on low-threshold, community-based conversations (e.g., in bars rather than at the doctor’s office) to reach men who otherwise rarely talk about health.
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FAQ: Low Testosterone
1. When should I get tested for low testosterone?
Dr. Christoph Keining: “ At the very latest when you start to feel: ‘I don’t feel the same as I used to; something isn’t right.’ That’s when it’s worth looking into the differential diagnoses: What’s causing the fatigue, the lack of energy, and the loss of libido?” Taken in isolation, a single symptom is not yet a cause for concern—it’s only when several symptoms occur together that it makes sense to seek a medical evaluation.
2. Does a high testosterone level make you aggressive?
Dr. Christoph Keining: " That's a myth: Too much testosterone doesn't make you aggressive. The opposite is true: A deficiency makes you irritable and aggressive."
3. Does testosterone replacement therapy increase the risk of a heart attack or prostate cancer?
Dr. Christoph Keining: "Recent studies have clearly refuted the claim that it increases the risk of prostate cancer or heart attack." On the contrary: An untreated deficiency significantly increases the risk of heart attack and stroke.
4. Can young men in their early 30s also have a genuine deficiency?
Dr. Christoph Keining: "Even young patients in their early 30s can have a genuine deficiency—this is often underdiagnosed because people say, 'You're still young; that can't possibly be the case for you.'" According to Keining, this even applies to patients who lead a healthy lifestyle.
5. What form of therapy does Dr. Keining recommend, and why?
Dr. Christoph Keining: “The problem with depot preparations is that the level rises very, very high at first... but then it drops just as low again... so it’s more like a roller coaster.” Instead of the traditional depot preparation (an injection every two weeks), he uses a testosterone ester that is injected twice a week. His conclusion: “This allows me to achieve true freedom from symptoms, not just relief.”
6. What is the main effect of testosterone, according to Dr. Keining?
Dr. Christoph Keining: " In my view, the main effect is psychological: it boosts dopamine production. Dopamine makes you want to get things done—the opposite of procrastination."
