Testosterone deficiency: symptoms, blood test, therapy and risks

What testosterone does in a man’s body

Testosterone is produced 95 percent in the testes, controlled by the pituitary gland via luteinising hormone. It governs libido and erection, sperm production, muscle growth, bone density, blood formation, fat distribution, mood and drive. Levels follow a daily rhythm with the peak in the early morning and fall by up to 30 percent by the afternoon. With age they decline slowly, about one percent per year from the age of 40; most men remain within the normal range.

A deficiency arises when the testes produce too little (primary hypogonadism), when control from the brain is lacking (secondary hypogonadism) or when overweight and chronic illness dampen the axis (functional hypogonadism). The last form is by far the most common and the only one that often resolves completely by treating the cause.

Symptoms: specific and non-specific

The European Male Ageing Study with over 3,000 men between 40 and 79 examined which complaints are actually related to low testosterone. Clearest were three sexual symptoms: fewer morning erections, less sexual desire and erectile dysfunction. They only clustered at values below 11 nmol/l, clearly below 8 nmol/l. Physical symptoms such as loss of strength and lower stamina were more weakly related, psychological ones such as tiredness and low mood hardly at all.

For you this means: lack of drive alone is not a testosterone problem. If sexual symptoms are added, the blood test is worthwhile. Further clues to a true deficiency are hot flushes, loss of body hair, breast growth, anaemia, unexplained bone loss and small, soft testes.

The blood test: done correctly or worthless

The Endocrine Society guideline is unambiguous: a deficiency is diagnosed only if symptoms are present and total testosterone is clearly low on two different days, measured in the morning between 8 and 10, fasting, outside acute illness. A single value, an afternoon value or a value during flu is not usable; up to 30 percent of men with a low first value have a normal one on the second test.

The harmonised lower reference limit for healthy young men is 9.2 nmol/l (264 ng/dl) according to Travison and colleagues. If the value is in the grey zone between about 8 and 12 nmol/l, sex hormone-binding globulin and free testosterone are also measured, because overweight, diabetes and thyroid disease change SHBG and thus the available fraction. LH and FSH show whether the cause lies in the testes or in the control system; prolactin and, if suspected, an MRI of the pituitary complete the assessment. Before therapy, PSA, blood count with haematocrit, liver values, lipids and blood sugar are added.

No guideline recommends screening men without symptoms. Advertised “testosterone checks” without symptoms and without medical interpretation lead to false diagnoses and unnecessary therapies.

Causes that can be treated

In most middle-aged men with low testosterone one of the following causes is found. Treating it is the first step, often the only one needed:

• Overweight. Fat tissue converts testosterone into oestrogen and dampens the control system. Losing 10 percent of body weight measurably raises the level; after bariatric surgery it frequently normalises completely.
• Type 2 diabetes and metabolic syndrome. Closely linked to overweight and insulin resistance.
• Sleep apnoea and lack of sleep. Testosterone is produced during deep sleep; untreated sleep apnoea lowers the level and worsens under testosterone therapy.
• Medicines and substances. Opioids, glucocorticoids, some antidepressants, excessive alcohol and above all anabolic steroids, which often shut down the body’s own production for months to years.
• Chronic diseases. Kidney and liver failure, HIV, chronic inflammatory diseases, iron overload.
• Diseases of the testes and pituitary. Klinefelter syndrome, undescended testes, mumps orchitis, chemotherapy, prolactinoma, tumours or irradiation of the pituitary; here therapy is usually needed permanently.

Therapy: benefits, forms, monitoring

With a proven deficiency, matching symptoms and no contraindications, the guideline recommends testosterone replacement therapy. The Testosterone Trials with 790 men over 65 showed what it achieves: a moderate improvement in sexual desire and activity, a slight increase in walking distance and mood, more bone density and correction of anaemia, but no effect on vitality and memory. Muscle mass increases, fat mass decreases, most clearly in combination with strength training.

Available are transdermal gels applied daily to shoulder or upper arm that produce even levels, and depot injections every 10 to 14 weeks. Gels carry the risk of transfer to partner or children through skin contact; washing hands and covering the area is mandatory. Testosterone, haematocrit and PSA are monitored after three and twelve months and then yearly; if haematocrit rises above 54 percent, therapy is paused or reduced.

Testosterone is not used with prostate or breast cancer, haematocrit above 50 percent, untreated severe sleep apnoea, marked prostate symptoms, severe heart failure and within six months of a heart attack or stroke. And when planning children: external testosterone suppresses sperm production, often for a long time. Men with deficiency who wish to have children are treated with other substances that stimulate their own production.

Cardiovascular safety: what TRAVERSE showed

For years it was unclear whether testosterone endangers the heart. The TRAVERSE trial largely answered this question in 2023: 5,246 men between 45 and 80 with proven deficiency and existing or impending cardiovascular disease received testosterone gel or placebo for an average of 22 months. Major cardiovascular events were not more frequent. More frequent, however, were atrial fibrillation, pulmonary embolism and acute kidney injury. With the right indication, therapy is therefore safe for the heart but not risk-free, and it does not replace treatment of blood pressure, lipids and weight.

Overweight, diabetes and testosterone: a vicious circle

Belly fat is hormonally active. It converts testosterone into oestrogen via the enzyme aromatase, releases inflammatory messengers and dampens control from the pituitary. Low testosterone in turn promotes the build-up of fat tissue and the loss of muscle, worsens insulin sensitivity and lowers the drive to exercise. A cycle arises in which overweight, type 2 diabetes and testosterone deficiency reinforce each other. Studies show that a weight loss of about 10 percent raises testosterone by an average of 2 to 3 nmol/l; after bariatric surgery it normalises completely in most men. With functional deficiency, weight loss is therefore the therapy of first choice, not replacement. It removes the cause, improves blood sugar and blood pressure at the same time and has none of the side effects of hormone therapy.

Anabolic steroids and the time afterwards

A growing proportion of young men with testosterone deficiency have taken anabolic steroids to build muscle. Testosterone or its derivatives supplied from outside switch off the body’s own production; after stopping, testes and control system need months to years to recover, and sometimes they do not recover completely. Typical complaints are loss of libido, erectile dysfunction, depressed mood, testicular shrinkage and infertility. Anyone who has taken anabolic steroids should say so openly in the consultation; it changes diagnosis and treatment, because replacement therapy would further delay recovery. Instead, substances that stimulate the body’s own production are considered, accompanied by endocrinological monitoring.

What you can do yourself

Strength training two to three times a week, seven to eight hours of sleep, weight loss if overweight, treatment of sleep apnoea, alcohol in moderation and abstaining from anabolic steroids measurably raise testosterone and improve exactly the complaints in question. Supplements help only with a proven deficiency of zinc or vitamin D. So-called testosterone boosters from the internet are either ineffective or contain undeclared hormones with considerable risks.

What the video consultation can do

The doctor at OpenClinic24 records your complaints in a structured way, checks medicines and pre-existing conditions, tells you which laboratory values are useful and when, and interprets existing results. If a deficiency is proven, they discuss causes, treatment options, monitoring and risks; with indications of a disease of the testes or pituitary or when planning children, you receive a referral to endocrinology or andrology. Therapy without a twice-confirmed deficiency is not started.