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Testosterone is a hormone which is responsible for many of the physical characteristics specific to adult males.It plays a key role in reproduction and the maintenance of bone and muscle strength.

Alternative names for testosterone

Testo (brand name for testosterone formulations); 4-androsten-17β-ol-3-one.

What is testosterone?



In women, testosterone is produced by the ovaries and adrenal glands. The majority of testosterone produced in the ovary is converted to the principle female sex hormone, oestradiol.

How is testosterone controlled?



What happens if I have too much testosterone?


In women, high blood levels of testosterone may also be an indicator of polycystic ovary syndrome. Women with this condition may notice increased acne, body and facial hair (called hirsutism), balding at the front of the hairline, increased muscle bulk and a deepening voice.

There are also several conditions that cause the body to produce too much testosterone. These include androgen resistance, congenital adrenal hyperplasia and ovarian cancer. 

The use of anabolic steroids (manufactured androgenic hormones) can lead to a perceived high level of testosterone by the hypothalamus, resulting in reduced luteinising hormone secretion from the pituitary gland and, in turn, a decrease in the amount of testosterone produced within the testes, while artificial testosterone levels remain high.  In men, prolonged exposure to anabolic steroids results in infertility, a decreased sex drive, shrinking of the testes and breast development. Liver damage may result from its prolonged attempts to detoxify the anabolic steroids. Behavioural changes (such as increased irritability) may also be observed. Undesirable reactions also occur in women who take anabolic steroids regularly, as a high concentration of testosterone, either natural or manufactured, can cause masculinisation (virilisation) of women.

What happens if I have too little testosterone?

If testosterone deficiency occurs during foetal development, then masculinisation of the foetus will fail to occur normally and this may give rise to disorders of sex development. If testosterone deficiency occurs during puberty, a boy’s growth may slow and no growth spurt will be seen. The child may also fail to develop full sexual characteristics (hypogonadism) associated with men undergoing puberty, including development of pubic hair, growth of the penis and testes and deepening of the voice. Around the time of puberty, boys with too little testosterone may also have less than normal strength and endurance, and their arms and legs may continue to grow out of proportion with the rest of their body.

In adult men, low testosterone may lead to a reduction in muscle bulk, loss of body hair and a wrinkled ‘parchment-like’ appearance of the skin. Testosterone levels in men decline naturally as they age. In the media, this is sometimes referred to as the male menopause (andropause).


 Reviewed: January 2015