Testosterone deficiency or hypogonadism (the medical term) is a condition where there is a reduction in the level of circulating testosterone in the body that leads to abnormal male sexual function and body development. Hypogonadism due to failure of the testes to produce adequate testosterone is called primary hypogonadism. When there is a failure of the pituitary gland (near the brain) to tell your testes to produce enough testosterone this is called secondary hypogonadism.
How common is testosterone deficiency?
Testosterone deficiency due to a clear biological cause is present in about 1 in 500 men or 0.2% of men. That means testosterone deficiency related to a problem of the testes or pituitary.
Another form of testosterone deficiency is associated with weight gain, advancing age, lack of exercise and chronic illness. This is sometimes called late onset hypogonadism because it usually starts after the age of 40. It is particularly hard to define and diagnose and is thought to affect 1 in 50 men or 2% of men.
What causes testosterone deficiency?
The causes of primary hypogonadism are related to the testes themselves and include:
- Damage to the testes (e.g. from trauma, infection, cancer, radiotherapy or surgery).
- Failure of the testes to descend from near your gut in your abdomen to the scrotal sac
- Klinefelter syndrome is a cause of primary hypogonadism where you are born with two female sex chromosomes and one male sex chromosomes (men are normally born with one female and one male sex chromosome – XY – and women are born with two female sex chromosomes – XX).
There are many causes of secondary hypogonadism.
- A prolactinoma is a hormone secreting tumour in the pituitary gland that destroys the gland itself and stops it from telling your testes to make more testosterone
- Damage to the pituitary gland (e.g. from a prolactinoma but also surgery or radiotherapy)
- Genetic disorders that affect the pituitary are a cause but they are rare
- Use of anabolic steroids suppressed your body’s natural testosterone production
- Use of opiates (morphine, heroin, and some other strong prescription painkillers) can also suppress testosterone production
Testosterone production also declines as you get older and the rate of this decline will increase if you are overweight, are not exercising regularly, if you develop diabetes or if you have some chronic illness. In fact testosterone levels in men can be considered are marker of health.
Why is testosterone deficiency a difficult diagnosis to make?
As a condition it is very difficult to define and diagnose for four main reasons.
- The symptoms of testosterone deficiency can also be caused by many other conditions that are much more common than testosterone deficiency
- The levels of testosterone naturally fluctuate over the course of the day and their measurement is dependent on other proteins in the blood as well as the instrument used to measure them. There is no consensus agreement on what the normal range for testosterone even is.
- The various symptoms caused by testosterone deficiency do not all occur at the same level some only occur when the levels are very low and others when the levels are slightly reduced. The level at which they occur also differs between people. So one person with a certain testosterone level might experience a symptom where as another person might not.
- Testosterone levels naturally decline in all men as they get older and also decline with weight gain and ill health
For these reasons it is difficult to diagnose testosterone deficiency and to be sure whether symptoms associated with testosterone deficiency aren’t caused by something else that is more common.
What are the symptoms of testosterone deficiency?
Classical symptoms of testosterone deficiency include
- Reduced libido
- Reduced frequency of spontaneous erections (e.g. erections early in the morning or ‘morning wood’)
- Reduced facial and body hair (e.g. reduced need to shave)
- Development of breast tissue.
Symptoms that may also be related to testosterone deficiency but are much more commonly caused by other conditions are
- Reduced energy levels
- Lower mood and motivation
- Increased body fat and decreased muscle.
If the testosterone deficiency starts as a baby there will be a very small penis and testes. If it starts prior to puberty there will be a failure of the body (including penis and testes) to sexually mature (e.g. small testes without the thickened scrotal skin that mature men have, a voice that has deepened and less facial, body and pubic hair).
How is testosterone deficiency diagnosed?
Testosterone deficiency can be diagnosed in men with typical symptoms (like those described above) by measuring levels of total testosterone in the blood on two separate occasions as well as measuring Leutenising Hormone (LH).
Normal testosterone could be considered to be between 8 – 27 nmol/L but there is no universal agreement on this. A level between 8 – 15 nmol/L may also be considered abnormal if the LH level is 1.5 times the upper limit of normal. LH is a hormone that tells your testes to produce more testosterone. It’s produced by the pituitary which is near the brain. If this hormone level is high it suggests your body is telling you it needs to make more testosterone.
The first step is to measure a total testosterone level in the blood first thing in the morning. Measuring first thing in the morning minimises the effect of fluctuation in your hormone levels over the course of the day. If the level is below 15 nmol/L a second test should be ordered, this time also testing LH. A diagnosis of testosterone deficiency can be made if the level is under 8 nmol/L on two occasions OR if the level is under 15 nmol/L on two occasions and the LH is 1.5 times the upper limit of normal.
When is further testing needed?
Further testing is often needed when diagnosing testosterone deficiency. Most of the testosterone is bound to proteins in the blood, namely sex hormone binding globulin (SHBG). Obesity, thyroid and liver conditions, diabetes and other chronic illness can change the levels of SHBG and this might make the testosterone in the blood seem artificially high or low.
If a primary or secondary hypogonadism is diagnosed then a cause should be sought. In primary hypogonadism for example a chromosome analysis should be performed because 1 in 500 men have Klinefelter’s syndrome. In secondary hypogonadism it is important to test for a prolactinoma in the pituitary. In late onset hypogonadism it is important to test for diabetes and exclude prescription or illicit drugs as a cause.