Low testosterone in men: symptoms, causes and treatment

Short answer: Low testosterone levels cause fatigue, loss of libido and muscle wasting. Diagnosis requires two blood tests as well as clinical symptoms. Testosterone replacement therapy is effective, but only in cases of confirmed hypogonadism.

Persistent tiredness, reduced sex drive or unexplained mood swings – many men attribute these symptoms to stress or the ageing process. However, low testosterone levels may be the actual cause. Testosterone is the most important male sex hormone and plays a role in almost every system in the body: from muscle mass and bone density to mood and sexual function. Fellos explains when your testosterone level is too low, how this is determined and what treatment options are available.

What are the symptoms of low testosterone levels?

The symptoms of low testosterone levels are often vague and overlap with other conditions, meaning they are regularly overlooked. The most common symptom is persistent tiredness combined with a lack of energy, even after sufficient sleep. In addition, men with a deficiency often suffer from a reduced libido. A low libido in men is one of the most frequently reported complaints during consultations for hypogonadism. Research shows that testosterone plays a direct role in mood, motivation and well-being, and that a deficiency leads to low mood, irritability and concentration problems.

Physically, low testosterone levels manifest as a loss of muscle mass and an increase in fat, particularly abdominal fat. A prolonged deficiency also leads to bone loss, which increases the risk of osteoporosis. Erectile problems also occur; although stress is another common cause of erectile problems, a hormone deficiency may be the underlying factor exacerbating the situation. As the symptoms are so vague, the diagnosis is often not made until years later.

What is a normal testosterone level?

In adult men, total testosterone is normally between 10 and 30 nmol/L, although different laboratories use slightly different reference ranges. A single measurement outside this range is not sufficient on its own to make a diagnosis. According to the Endocrine Society guidelines, hypogonadism is only diagnosed when two separate blood tests fall below the reference value, combined with existing clinical symptoms.

The timing of the measurement is crucial: testosterone levels follow a circadian rhythm with a distinct peak in the early morning. A measurement taken later in the day can result in a falsely low value. In addition to total testosterone, free testosterone is also relevant – this is the biologically active fraction that is not bound to SHBG or albumin. In men with high SHBG levels, total testosterone may appear normal, whilst free testosterone is too low, which explains the symptoms.

What are the causes of low testosterone levels?

Doctors distinguish between two main forms of hypogonadism. In primary hypogonadism, the problem lies in the testicles themselves: damage caused by infection, surgery or radiation, or congenital conditions such as Klinefelter’s syndrome or cryptorchidism. A review article in The Lancet describes the pathophysiology of primary hypogonadism as a direct disruption of testosterone production in the Leydig cells.

In secondary hypogonadism, the problem lies further up the hormonal axis: the hypothalamus or pituitary gland sends insufficient signals to the testicles. Causes include a pituitary tumour, trauma or chronic diseases. Obesity plays a particular role: Adipose tissue converts testosterone into oestrogen via the enzyme aromatase, creating a negative feedback loop that further suppresses production. In addition to structural causes, lifestyle factors also play a part: chronic stress increases cortisol levels, which blocks testosterone, whilst lack of sleep and excessive alcohol consumption disrupt the hypothalamic-pituitary axis. After the age of 30, testosterone levels decline by an average of 1 to 2 per cent per year – a gradual process which, on its own, rarely leads to clinical hypogonadism, but which, in combination with other factors, can certainly cause symptoms.

How is a low testosterone level diagnosed?

Diagnosis begins with a blood test: total testosterone, LH, FSH and SHBG are measured. Free testosterone can be calculated using SHBG and albumin. As already described, two measurements on different days are required, preferably in the morning on an empty stomach. The American Urological Association recommends that, in the event of abnormal values, a second measurement should always be carried out before the diagnosis is confirmed.

LH and FSH provide information about the cause: high levels indicate primary hypogonadism, low levels a secondary cause. If a pituitary disorder is suspected, a supplementary imaging examination is carried out. The Pharmacotherapeutic Compass emphasises that a diagnosis may only be made if both low blood levels and corresponding symptoms are present – an isolated low value without symptoms does not justify treatment.

What are the treatment options for low testosterone levels?

In cases of confirmed hypogonadism, testosterone replacement therapy is the most effective treatment. Clinical studies show that replacement therapy improves bone density, increases muscle mass, reduces fatigue and restores libido in men with a confirmed deficiency. The most commonly used form of administration in the Netherlands is a transdermal gel, such as Androgel. The starting dose is 5 grams of gel (50 mg testosterone) once daily, preferably applied in a thin layer to the shoulders or arms in the morning. Allow to dry for at least three to five minutes after application, then wash your hands. You should wait at least one hour before showering or swimming. Through the testosterone treatment at Fellos, you will undergo an online consultation, following which a Dutch doctor will assess your blood test results and draw up a treatment plan.

In addition to medication, lifestyle changes can have a significant effect in cases of mild deficiency. Weight loss reduces aromatase activity in fatty tissue, meaning less testosterone is converted into oestrogen. Getting enough sleep restores the night-time testosterone peak. Stress reduction normalises cortisol levels, thereby reducing the negative inhibition of testosterone. If you want to increase your sex drive, it is worth addressing lifestyle factors first before resorting directly to medication.

What are the risks of testosterone treatment?

Testosterone replacement therapy is safe when used correctly, but requires medical supervision and regular blood tests. The most common clinically relevant side effect is polycythaemia: an increase in the number of red blood cells, which raises the risk of blood clotting. Blood tests are therefore mandatory at the start of and during treatment. With long-term use, the body’s own sperm production also decreases, as the body produces less LH due to negative feedback.

Testosterone treatment is absolutely contraindicated in men with prostate cancer or breast cancer. Transmission via the skin to a partner or children is possible as long as the gel has not completely dried; this requires caution during physical contact. Testosterone gel as a treatment option is intended exclusively for men with a proven hormone deficiency, not as a performance-enhancing agent or anti-ageing therapy. If you have any doubts about suitability, you should always discuss this with a doctor.

Do you recognise these symptoms? Have your testosterone levels checked

Low testosterone is a treatable condition, provided the diagnosis is correct. Through Fellos, you’ll complete an online assessment, receive a blood test kit, and a Dutch doctor will assess whether testosterone therapy is suitable for you. Start the online assessment and find out if a hormone deficiency explains your symptoms.