Testosterone deficiency: Impact on health, therapeutic approaches and prevention – Insights from Dr. Christian Leiber-Caspers
A testosterone deficiency is associated not only with reduced libido and erectile dysfunction, but also with other symptoms. The reason: The sex hormone testosterone is involved in important physiological processes such as energy metabolism and muscle building. To support quality of life and psychological well-being, the combination of a healthy, active lifestyle with hormone replacement therapy has proven effective.
serotalin®: Dr. Leiber-Caspers, how does testosterone deficiency affect men's sexual health and fertility?
Dr. Leiber-Caspers: Testosterone is the central male sex hormone and therefore has a clear impact on sexuality. A testosterone deficiency can manifest itself in various symptoms. A common first sign is a declining libido—a decrease in sexual desire. This can occur even when testosterone levels are only at the lower end of the normal range. Severely reduced or persistently low testosterone levels can also lead to erectile dysfunction, although these are usually indirectly related to the hormone deficiency.
Testosterone is essential for fertility because it is needed for sperm production. Long-term, very low testosterone levels can therefore lead to reduced sperm production and thus to fertility problems. However, very high testosterone levels are also problematic: In high doses, testosterone acts like a contraceptive because it can suppress sperm production. This principle has been investigated in studies, including a WHO study in which men were given high doses of testosterone. A significant reduction in sperm production was observed – in many cases, this even led to infertility. However, this method has not yet become established as a "male pill," and corresponding studies have been discontinued.
serotalin®: What role does testosterone play in the different phases of a man's life, especially with regard to andropause?
Dr. Leiber-Caspers: As an andrologist, I don't use the term "andropause" because it's misleading. Unlike menopause in women, which is accompanied by an abrupt drop in hormones, hormonal development in men follows a fundamentally different course. It's often assumed that testosterone levels automatically decline with age, and that an older man has only half the testosterone level of a 20-year-old. However, this is not consistent with scientific evidence.
Large studies with over 10,000 participants show that men can still have high testosterone levels at the age of 60, 70, or even 80. The decline is therefore not inevitable. Rather, it is associated with concomitant diseases and certain lifestyle factors that influence testosterone levels. For example, obesity, diabetes, or chronic illnesses can lower testosterone levels. However, those who lead a healthy lifestyle and pay attention to certain aspects can maintain stable and sufficient testosterone levels even in old age.
serotalin®: What diagnostic procedures do you use to detect and assess testosterone deficiency?
Dr. Leiber-Caspers: The diagnosis of testosterone deficiency begins with a thorough medical history, i.e., taking the patient's medical history, as well as a systematic recording of the patient's symptoms and complaints. For this purpose, we use, among other things, standardized questionnaires, such as the "Aging Males' Symptoms Score" (AMS). This contains 17 different questions on areas such as concentration, erectile function, libido, physical strength, and mood swings. The patient rates their complaints on a scale of 1 to 5. The AMS score is used in many studies, but is not sufficient on its own to diagnose testosterone deficiency, as similar symptoms can also be caused by other reasons—such as the flu or general exhaustion. Nevertheless, the AMS score can be helpful in monitoring the course of therapy, as an improvement in symptoms can be expected.
According to the guidelines of the European Urological Association (EAU), the actual diagnosis is made by determining the total testosterone level in the serum. It is important that the measurement be performed twice on different days, as testosterone is subject to natural fluctuations. For example, the level is usually highest between 8 and 10 a.m., so the blood sample should be taken at this time, ideally on an empty stomach. A reliable diagnosis of testosterone deficiency can only be made when both clinical symptoms and two independent measurements outside the normal range are present.
serotalin®: Can you explain how testosterone replacement therapy can affect general well-being and physical performance?
Dr. Leiber-Caspers: Testosterone is not only a sex hormone, but also fulfills many other important functions in the body. It influences drive, energy levels, and overall performance. A severe testosterone deficiency can therefore be accompanied by symptoms such as listlessness, fatigue, depression, and a general decline in performance. When testosterone levels are restored to normal through replacement therapy, many patients report a noticeable improvement in their well-being, increased energy, and an improved quality of life.
Testosterone also has an anabolic, muscle-building effect. While this effect is often associated with doping or anabolic steroids, it also plays a role in medical applications. Many men with testosterone deficiency exhibit an unfavorable body composition: they lose muscle mass and gain increased abdominal fat. Testosterone replacement therapy can help here, especially in combination with a healthy diet and regular physical activity. It is important to note that testosterone alone does not work miracles—it should always be combined with an active lifestyle. Studies show that men with balanced testosterone levels, combined with regular training, have a better body composition, greater strength, and increased physical performance.
serotalin®: How do you assess current developments and trends in testosterone therapy? Are there any new findings or therapies?
Dr. Leiber-Caspers: Currently, there are no new therapeutic approaches approved in Germany or Europe. The two established methods of testosterone replacement therapy remain unchanged: transdermal application via the skin in the form of gels that can be individually dosed, and intramuscular depot injections, which are administered at longer intervals. Both forms of therapy have proven effective, and there are currently no groundbreaking new developments.
An important aspect of testosterone therapy concerns patients who take opioids for pain management long-term. These patients may develop a condition called opioid-induced hypogonadism syndrome, in which testosterone production is inhibited by chronic pain medication therapy. This is a relevant clinical point to consider in these patients.
In terms of safety aspects, the risk of cardiovascular disease is well documented and is subject to critical debate. However, current data shows that correctly administered testosterone therapy does not generally carry an increased risk of heart disease. However, careful individual consideration should be given to patients with pre-existing cardiac conditions. Another frequently discussed topic is the connection between testosterone and prostate cancer. Extensive data show that testosterone therapy does not pose an increased risk of prostate cancer in patients with a diagnosed deficiency. In fact, men with testosterone deficiency benefit from treatment – also with regard to prostate health, since normalizing hormone levels is often accompanied by a reduction in typical symptoms.
serotalin®: In which cases do you advise against testosterone therapy and what alternative treatment options are there?
Dr. Leiber-Caspers: There are clear contraindications for testosterone therapy. These include:
- Untreated prostate cancer or breast cancer in men : These diseases are directly related to hormonal changes, which is why testosterone therapy is excluded in such cases.
- Polycythemia (high hemoglobin or hematocrit levels in the blood) : Testosterone can stimulate blood formation, which can increase the risk of thrombosis or cardiovascular complications.
- Severe, untreated prostate enlargement requiring surgery : In such cases, further stimulation with testosterone may be problematic.
- Acute cardiovascular events : Men who have recently had a heart attack or stroke should not be treated with testosterone initially because the risk of complications may be increased.
- Men who clearly want to have children: Testosterone therapy suppresses the body's own sperm production and thus impairs fertility.
Alternative treatment options: Drug Alternatives are difficult to find, as a true testosterone deficiency cannot simply be replaced with other medications. In rare cases—particularly when the problem lies in the pituitary gland and the testicles are insufficiently stimulated—treatment with stimulating hormones may be considered. However, this therapy is only relevant for a small group of patients.
It's important to note that testosterone therapy should not be used for lifestyle reasons. Men with normal testosterone levels should not receive testosterone under any circumstances – neither as an anti-aging agent nor to enhance performance, as this is not medically justified and is also prohibited in sports as doping.
In some cases, lifestyle changes can be a sensible alternative. For example, being severely overweight can lower testosterone levels. A patient who weighs 150 kg and has significant abdominal fat could positively influence their hormone balance through significant weight loss. Regular exercise, a healthy diet, and sufficient sleep are important factors that can also affect testosterone levels.
serotalin®: How is testosterone level related to the risk of other diseases, such as cardiovascular problems or osteoporosis?
Dr. Leiber-Caspers: A testosterone deficiency can have long-term effects on bone health, particularly with regard to osteoporosis. The key factor here is not testosterone itself, but the hormone estradiol, which is formed from testosterone in men. If testosterone levels are too low for an extended period, insufficient estradiol can be produced, leading to reduced bone density. The risk of pathological fractures increases – often without the affected person noticing it early on. Only a bone density test then reveals a sometimes drastic reduction in bone density. If testosterone deficiency is treated, however, it takes several years for bone stores to be sufficiently replenished. Therefore, it is important to regularly monitor bone health in cases of long-term deficiency – as recommended by medical guidelines.
The connection between testosterone and cardiovascular disease is controversial. In the past, there have been warnings that testosterone therapy could potentially increase the risk of heart problems – primarily based on older studies from the USA, which, however, are methodologically controversial. More recent studies show the opposite: Men with testosterone deficiency have an increased risk of death, partly due to a higher susceptibility to cardiovascular disease. Low testosterone levels could therefore be a risk factor for heart problems.
This is particularly evident in prostate cancer patients who are treated with androgen deprivation therapy (androgen deprivation therapy) to achieve near-zero testosterone levels. After just one year of this treatment, the risk of heart attacks and strokes increases significantly. This suggests that testosterone in normal amounts has a protective rather than damaging effect on the cardiovascular system.
serotalin®: What preventative measures can men take to maintain healthy testosterone levels or counteract a decline?
Dr. Leiber-Caspers: There are some clear steps men can take to stabilize their testosterone levels long-term and counteract a decline. A healthy lifestyle plays a key role in this.
- Healthy diet: A balanced diet with sufficient protein, healthy fats, and micronutrients such as zinc and vitamin D is essential for testosterone production. Highly processed foods and excessive sugar consumption should be avoided.
- Maintain a normal body weight: Obesity, especially excessive abdominal fat, negatively impacts testosterone levels. Fatty tissue contains the enzyme aromatase, which converts testosterone into estrogen. Increased levels of female hormones can, in turn, have negative effects on male hormone balance and the cardiovascular system. Since over 50% of men over 50 in Germany are overweight, there is great potential for prevention.
- Regular physical activity: Strength training, in particular, has been proven to have a positive effect on testosterone levels. A balanced ratio between strength and endurance training is optimal. Studies show that a mix of about one-third strength training and two-thirds moderate endurance exercise has the best effect. However, those who engage in excessive endurance exercise, such as marathon runners, tend to have lower testosterone levels. Sprinters or athletes with a balanced training schedule, on the other hand, have stable and healthy testosterone levels.
- Adequate sleep: Lack of sleep has a direct negative impact on testosterone production. Men should try to establish a regular sleep routine and sleep 7–9 hours per night. Shift workers or people with constantly changing sleep patterns are particularly at risk for testosterone deficiency.
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Avoid drugs and excessive alcohol consumption: Drugs or excessive alcohol consumption can inhibit testosterone production. Certain medications, especially opioids or long-term cortisone therapy, can also negatively affect testosterone levels.
In summary, a healthy lifestyle with a balanced diet, a stable body weight, regular physical activity and sufficient sleep are the best measures to maintain healthy testosterone levels.
About the author: Dr. Christian Leiber-Caspers is the head of the Andrology Section at the Department of Urology at the Alexianer Hospital in Krefeld. As a urologist with a specialization in andrology, his areas of expertise include erectile dysfunction, anatomical malformations, and genital microsurgery. Within the scope of sexual medicine, the urologist, who is a member of the German Society for Andrology and Urology, also specializes in topics such as drug-based tumor therapy.
In addition, Dr. Leiber-Caspers is chairman of the Information Center for Sexuality and Health (ISG) and a member of the board and elected president for the 2026 annual congress of the German Society for Andrology (DGA).
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