Testosterone is the primary male sex hormone.

It is responsible for male sexual characteristics, including hair growth distribution, bone structure, muscle growth, deep voice, prostate and testes development. It affects behaviour, including aggression, courtship, risk-taking and sex drive. It can also affect mood.

Ninety five percent of testosterone is produced in the testes and 5% is produced in the adrenal glands. Testosterone is a steroid hormone, like estrogen, progesterone and cortisone. Its unique chemical structure makes it the main androgenic hormone in the human body. Estrogen and progesterone are the dominant female hormones.

While being a distinctly male hormone, females also produce some testosterone. Males produce about 10 to 20 times more testosterone than females and, in females, it is responsible for bone and muscle development and partially responsible for sex drive.

Testosterone production is highest in males between their late teens and early 20s. High levels of the hormone at that age are responsible for the rapid development of male characteristics. And the development of overactive skin sebaceous glands as well as the development of teenage acne. Levels remain high until the mid-30s, when they start to decline. The decrease rate is about 1% to 2% per year.

Up to 25% of males may have low or sub-optimal testosterone levels. Andropause is........

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