The Male Hormone Testosterone

What is testosterone and what does it do?

Testosterone is a male sex hormone also known as an androgen. Testosterone produces changes in body shape and sexual characteristics typical of men after puberty and maintains adult male features and stimulates the testes to produce sperm. Androgens play a major role in the reproductive and sexual function of the adult male. The equivalent sex steroid produced by women is oestrogen.

Testosterone is also important for the growth of bones and muscles and stimulates the bone marrow to make red blood cells as well as affecting mood and libido. It is secreted in a circadian rhythm. Testosterone is produced in the testes under the control of Luteinising Hormone (LH) that is secreted by the pituitary gland. Testes also produce sperm that is under control of both FSH, also secreted by the pituitary gland, and testosterone produced in the testes (but not by exogenous testosterone – injections or topical solutions, which does not stimulate spermatogenesis). This means that the body’s natural production of testosterone is involved with sperm production, but any external testosterone treatment will suppress sperm production.

Testosterone or androgen deficiency

Androgen deficiency is a condition in which tissues do not have enough exposure to androgens with normal function. Low testosterone is also known as hypogonadism and may be the result of primary (testes) and secondary (brain) causes. Primary causes arise from the testes and secondary causes arise from the pituitary region of the brain. Primary hypogonadism can be seen in young men with Klinefelter’s syndrome which results from an extra sex chromosome (XXY). Primary hypogonadism can also occur in cases of undescended testes or when the testes have been removed either due to trauma, inflammation or cancer treatment. Ageing also decreases the function of the testes, as does long term alcohol consumption.

Secondary hypogonadism may arise from chronic health conditions such as haemochromatosis, sarcoidosis or a tumour of the pituitary gland called prolactinoma. A chronic health condition such as obstructive sleep apnoea may also impact on the testosterone level resulting from changes at the pituitary level.
Total testosterone in the blood is a measure of testosterone lightly bound to albumin and closely bound to sex hormone binding globulin (SHBG) as well as free testosterone. Sex hormone binding globulin increases with ageing but decreases with obesity. Levels of testosterone are highest in men between the ages of 20 and 30 years and fall gradually with age about 0.3% per year after the age of 40. About 1 in 200 men under 60 years of age suffer from androgen deficiency. However at the age of 65 years 10% of men are deficient in androgen and this increases to 20% by 70 years. Men’s testosterone levels fall much more gradually and over a longer period of time, unlike women, whose oestrogen levels fall rapidly when they go through the menopause.

Symptoms of testosterone deficiency

Deficiency of testosterone can present as reduced libido, decreasing size of the testes, absence of sperm, hot flushes and sweats, reduced shaving and enlargement of the breasts. Non specific signs and symptoms consist of decreased energy and increased fatigue, depressed mood, reduced muscle mass and strength, reduced bone density, poor concentration and memory, sleep disturbance and increasing body fat. Low testosterone may also contribute to erectile problems though androgen deficiency is an uncommon cause of this.
Late onset hypogonadism (LOH) also known as adult onset hypogonadism is a controversial diagnosis where the levels of testosterone that naturally fall with age are somewhat accelerated. As men age, the amount of body fat increases and muscle mass and strength decreases. A fall in testosterone levels is likely to contribute to these conditions. However any medical condition can accelerate this decline such as diabetes or obesity and the current recommendations are to treat the secondary causes first before considering treating the low testosterone with medication. It is important to note that sleep apnoea may be associated with low testosterone, it is always important to treat the sleep apnoea first before consideration of a testosterone treatment program. Any components of metabolic syndrome which include diabetes, obesity, high blood pressure and high cholesterol should always be treated first. These significant medical illnesses that can cause a fall in the level of testosterone usually recover when the illness has been treated.

Another name for LOH is “male menopause” and again, due to the controversy surrounding this condition, it is not regarded as a legitimate diagnosis. However replacing testosterone in older men who have a proven and documented very low testosterone has been shown to have a number of benefits on body fat, muscle, cholesterol and bone density as well as an improvement in quality of life.

How is low testosterone diagnosed

Low testosterone is diagnosed by assessment of clinical symptoms, physical examination and investigations. The testes may be reduced in size. Blood tests addresses LH, FSH, total testosterone, sex hormone binding globulin, prolactin and calculated free testosterone as well as thyroid and iron stores (ferritin).

In Australia the level of testosterone that can be treated to obtain a subsidised authority prescription is less than 6nmol/L or higher if the LH is raised. It should be noted that in other parts of the world this level is higher though it is possible in Australia to treat testosterone with a private prescription if the clinical and biochemical assessments concur with a diagnosis of hypogonadism.

How is low testosterone treated

There are many different types of medications and these include oral tablets, injections, patches, creams and gels. Treatment with testosterone must always be monitored as there is a risk of increasing the blood thickness (hematocrit) and aggravating sleep apnoea though there is no evidence that testosterone may result in prostate cancer. Testosterone treatment is usually continued for life.

Illegal products

Finally a word of warning about the illegal use of testosterone and related steroid medications, which are often obtained through the black market for the purposes of muscle enhancement in a gym setting. These medications may not be genuine and thus increase the risk of further health problems. They will also suppress the body’s own natural production of testosterone which may take 6 to 12 months to recover, or in some instances, never recover, thus then requiring life time testosterone supplementation.