Low testosterone: symptoms, causes, diagnosis and treatment

In adults, Patient.info lists erectile dysfunction, infertility, less beard and body hair, reduced muscle mass, breast tissue development and loss of bone density. In older men, it describes symptoms that resemble the menopause: excessive tiredness, lower sex drive, difficulty concentrating and hot flushes.

The NHS trust leaflet gives a similar list, adding depression or anxiety, irritability, reduced exercise tolerance and strength, night sweats, and memory problems. Crucially it warns that other conditions can cause these symptoms, so testosterone treatment may not improve all of them.

The NHS erectile dysfunction page is a useful reminder of that overlap. It says occasional erection problems are usually caused by stress, tiredness or too much alcohol, and that frequent problems may be linked to high blood pressure, high cholesterol, diabetes, depression or anxiety, or hormone problems.

The NHS 'male menopause' page lists symptoms that men in their late 40s to early 50s may develop: depression, loss of sex drive, erectile dysfunction, mood swings and irritability, loss of muscle mass and reduced ability to exercise, fat redistribution such as a larger belly or gynaecomastia, a general lack of enthusiasm or energy, difficulty sleeping or increased tiredness, and poor concentration and short-term memory. It stresses that in many cases the symptoms are nothing to do with hormones.

Testosterone is the most important sex hormone in men. Patient.info explains that its production is controlled by both the brain and the testicles, that production begins in puberty, and that from about the age of 30 levels usually start to decrease.

The North Cumbria Integrated Care leaflet defines hypogonadism as the medical term for testosterone deficiency and says it happens when the testes do not produce an adequate level. The problem can lie in the testes themselves or in the pituitary gland that controls them. It says low testosterone can occur at any age, alongside a gradual decline as men get older.

Patient.info says testosterone deficiency is more common in older men, in men who are overweight and in men with poor general health or long-term conditions. In one large European study it affected about 2 in 100 men aged 40 to 79 and about 5 in 100 men aged 70 to 79.

The NHS says the "male menopause" (sometimes called the andropause) is an unhelpful term sometimes used in the media. It says the label is misleading because it suggests the symptoms are the result of a sudden drop in testosterone in middle age, similar to the female menopause, and that this is not true. Although testosterone levels fall as men age, the NHS says the decline is steady at about 1% a year from around the age of 30 to 40, and this is unlikely to cause any problems in itself.

A testosterone deficiency that develops later in life, also known as late-onset hypogonadism, can sometimes be responsible for these symptoms, but the NHS says in many cases they are nothing to do with hormones. It describes late-onset hypogonadism as an uncommon and specific medical condition that is not a normal part of ageing, particularly in men who are obese or have type 2 diabetes, and says diagnosis can usually be made based on symptoms and blood tests that measure testosterone.

The NHS lists other possible causes of similar symptoms: stress, depression, anxiety, lack of sleep, a poor diet, lack of exercise, drinking too much alcohol, smoking and low self-esteem. If you have these symptoms the NHS advises seeing your GP, who will ask about your work and personal life to see if a mental health issue such as stress or anxiety may be responsible, and may order a blood test to measure testosterone. If results suggest a deficiency, you may be referred to an endocrinologist.

Treatment depends on the cause. For men without another underlying cause, Patient.info says maintaining a healthy body weight is important. The NHS trust leaflet says that once an underlying cause is addressed the level usually normalises, and that testosterone replacement may be considered if the body does not make enough and reversible causes are excluded. It is started by an endocrinologist.

Patient.info says replacement is usually given as a gel, with long-acting injections and skin patches as other forms. The NHS trust leaflet says the choice depends on risks, benefits, lifestyle and preference. Testosterone is a prescription-only medicine, so decisions on whether and how to use it belong with your specialist.

Monitoring is part of treatment. The trust leaflet says people are usually monitored annually once established, with blood tests including a full blood count, liver function, testosterone level and PSA. If the red cell count rises, the dose or form may be changed, and treatment is stopped if it stays high; it may also be stopped if PSA rises or prostate cancer is suspected.

• Side effects named by Patient.info include worsening sleep apnoea, acne, prostate enlargement, growth of existing prostate cancer, breast enlargement, shrinking testicles and lower sperm count, and over-production of red blood cells that can raise clot risk.

• Patient.info says replacement is not allowed in men with male breast cancer, prostate cancer, severe heart failure, a very raised haematocrit, or who want to conceive in future.

• The trust leaflet says the effect of treatment on cardiovascular risk is controversial but that it is known to raise the risk of venous thrombosis, especially in overweight and obese people.

Patient.info says testosterone deficiency can be identified by blood tests, which might be suggested when someone describes reduced libido or erectile dysfunction, and that men who do not respond to erectile dysfunction medicines should also have their level checked. It notes that many older men with low testosterone are never diagnosed because the symptoms are put down to ageing.

The NHS trust leaflet says the blood sample should be taken in the morning, preferably after overnight fasting, and that treatment is considered when testosterone is low on at least two occasions along with symptoms. Testosterone follows a daily rhythm, which is why a single random reading can mislead.

If a low level is confirmed, Patient.info says referral to a urologist or andrology specialist is usual. Further tests can include other hormone levels, semen analysis, a pituitary CT or MRI scan, genetic tests and sometimes a testicular biopsy.

Patient.info splits causes into two groups. In primary deficiency the testicles fail to make enough testosterone, with causes including Klinefelter's syndrome, undescended testicles, mumps orchitis, haemochromatosis, injury, and chemotherapy or radiotherapy. In secondary deficiency the testicles are normal but the pituitary or hypothalamus is not signalling to them properly, as with pituitary tumours such as prolactinoma, HIV, and some medicines including opiate painkillers.

Being significantly overweight or obese is linked to low testosterone at any age according to Patient.info. It adds that physical illness, surgery or emotional stress can reduce testosterone temporarily, with the level returning to normal once the problem has been treated. The NHS trust leaflet adds excess alcohol and previous anabolic steroid or testosterone injection use to the causes of a low reading.

Patient.info describes the evidence on replacement as mixed. It cites a 2016 review of more than 150 studies that found no evidence of benefit for heart disease and no consistent benefit for mood or cognition, with later reviews more positive for libido and mood. It adds that testosterone alongside erectile dysfunction medicines may help men who did not respond to those medicines alone.

The NHS trust leaflet lists possible benefits as improved sex drive, mood, muscle mass and strength, bone strength and red cell count, while stressing symptoms may not all improve. Fertility is a special case: Patient.info says replacement is not suitable for men who want to conceive, and other treatments may help when the cause lies in the pituitary.

On the NHS, a GP can assess symptoms, arrange morning blood tests and refer you to an endocrinologist or urologist if testosterone deficiency is suspected, and treatment is started and monitored by the specialist team. Some men choose a private endocrine or men's health consultation for faster appointments. In either setting the same principles apply: confirm low levels on repeated morning blood tests, look for reversible causes, discuss risks and benefits, and arrange regular monitoring. Results and treatment should be shared with your GP.