Testosterone is a steroid hormone produced in the testes, and it is found in mammals. Some testosterone is also produced in the adrenal gland and the normal levels of testosterone range from 7.7-31.4 nmol/L in males, which are about 8 times more than in females.

In men testosterone is responsible for male reproductive organs such as the testis and prostate, but also plays a major part in promoting secondary sexual characteristics for example muscle, bone mass and body hair.

When puberty occurs about the age of twelve years there is an increase in testosterone production which rises steeply until the age of between fifteen and seventeen years of age and a further rise in testosterone occurs in the twenties.

Testosterone levels peak around 6.0 am, and it is therefore important to measure levels of testosterone in the morning around 9.0 am.

Testosterone levels can decline in men from the age of fifty years, and free testosterone, the active 2% of unbound testosterone, declines by 1% per year from age fifty years.

Illness and stress can also cause a decline in testosterone levels, together with a lowered adrenal function, all are common causes of tiredness, which are frequently associated with lowered testosterone and DHEA levels.

The male andropause is often associated with a low free testosterone level, and a trial of testosterone replacement for three months, in the case of low levels, is often beneficial. Other causes do however need to be ruled out such as low sex drive, lethargy, tiredness, and erectile dysfunction.

Guidelines of the male andropause were published in the Aging Male journal in 2002, by Professors’ A. Morales and Lunenfeld, and in a recent presentation, Dr D.Kelly of Sheffield University stated “We know men with low testosterone are at greatly increased risk of type two diabetes and cardiovascular disease”. Testosterone is therefore an important factor in preventative medicine, in men with declining testosterone levels.

Careful monitoring of testosterone levels, together with PSA and haematology are important if men are given testosterone replacement therapy (T.R.T.) as levels should always be kept within the normal physiological range. A few men also aromatise testosterone to oestrogen, and if oestrogen levels are too high this will need to be monitored and treated.

Bio-identical testosterone is obtained primarily from soya beans and wild yams. They are pharmaceutically converted in the laboratory to the human bio-identical form and if in a gel or cream form are applied to the skin.

Other forms of TRT include intramuscular injections of testosterone that last for between six and eight weeks.


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