What causes low testosterone?

There are two main types of low testosterone conditions, and each has its own cause: these are referred to as primary and secondary hypogonadism. In addition to that there is another type of low testosterone that appears in aging men. This is considered as a combination of primary and secondary hypogonadism.

Primary hypogonadism

In primary hypogonadism, low testosterone is caused by a problem with the testes.

Secondary hypogonadism

Secondary hypogonadism occurs when the complex hormonal system responsible for producing male sex hormones goes out of balance or breaks down.

Late-onset hypogonadism

Late-onset hypogonadism refers to low testosterone associated with advancing age. Men normally experience some decline in testosterone level as they age due to reduced function of the tests and the complex hormonal system. This decline may be accelerated by poor health, and some men’s testosterone levels may fall too far.

About 20% of men older than 60 years and 30-40% of men older than 80 years have testosterone levels below the physiological range for younger men.

Age related decline in testicular function

What are risk factors for low testosterone?

Risk FactorDescription
Klinefelter's syndrome
A genetic deficiency in testosterone production. Affects between 1 in 500 and 1 in 1000 men.
Injury to the testes
The testes are prone to injury because they hang outside the body and are not protected by bone or muscle. Damage to testes can cause reduced testosterone production.
Un-descended testes
The testes develop within the abdomen and descend into the scrotum shortly before birth. In some cases one or both of the testes may not descend at birth (this happens in about 1 in 4 boys born prematurely and 1 in 20 boys born at term). The condition usually corrects itself naturally within the first year of life but if not corrected in early childhood, the testes may not develop properly.
Mumps orchitis
Sometimes a mumps infection will involve the testes as well as the saliva glands. If this happens during adolescence or adulthood, long-term damage may occur that affects testosterone production.
Cancer and cancer treatment
Cancer of the testes or pituitary tumours can lead to low testosterone. Chemotherapy or radiation therapy can also interfere with testosterone production.
Hormone system imbalance
Kallmann syndrome involves abnormal development of the hypothalamus and is a risk factor for low testosterone. Pituitary disorders can impair the release of hormones affecting normal testosterone production.
Chronic illnesses
Chronic illnesses such as liver or kidney disease, diabetes, metabolic syndrome and rheumatoid arthritis may be risk factors for low testosterone.In some instances it is not clear whether the chronic illness is a cause or a consequence of low testosterone.
Normal aging
Men normally experience some decline in testosterone level as they age.
Haemochromatosis is a genetic disorder that causes the body to absorb too much iron from the diet. This iron can be deposited in various body organs including the hypothalamus, pituitary and testes. It is now recognized as a common disorder and 1 in 200 people in Northern Europe may be at risk of developing iron overload.