Male-pattern baldness is the most common type of hair loss, affecting 6.5 million men in the UK.

It generally starts with a little thinning of the hair, followed by wider hair loss, allowing more of the scalp to become visible.

For a few men, this process starts as early as the late teens. By the age of 60, most men have some degree of hair loss.

Some men aren't troubled by this at all. Others, however, suffer great emotional distress associated with a lack of self-esteem, and in some cases depression.

"Young men especially feel hair loss pretty acutely," says Dr Susan McDonald-Hull, a consultant dermatologist at Mid Yorkshire Hospitals NHS Trust.

Male-pattern baldness is usually inherited and also affects women. It's caused by oversensitive hair follicles. Dihydrotestosterone (DHT) is produced by the male hormone testosterone, and it causes the follicles to shrink and eventually stop functioning. 

The involvement of testosterone in balding has led to the myth that going bald is a sign of virility. But men with male-pattern baldness don't have more male hormones than other men. Their hair follicles are simply more sensitive to the hormones.

Receding hairline

Male-pattern baldness is so called because it tends to follow a set pattern. The first stage is usually a receding hairline, followed by thinning of the hair on the crown and temples.

When these two areas meet in the middle, it leaves a horseshoe shape of hair around the back and sides of the head. Eventually you may go completely bald.

Male-pattern baldness is not a disease, so it won't affect your health. However, if it's causing you distress, consult your GP to get a diagnosis.

Your GP can refer you to a dermatologist for further analysis and, if necessary, to a psychologist to help with the trauma of hair loss.

If you have inherited the genes responsible for male-pattern or female-pattern baldness there's little you can do to prevent it from happening.

Treatments can slow down the process, but there's no cure. The two most effective treatments for male-pattern baldness (also called androgenetic alopecia) are:

• Minoxidil: this is available as a lotion that you rub on your scalp every day. The balding process slows in about 50% of men who use it, and 15% of users will experience hair regrowth. However, about a third of men don't see any change to their hair loss. Side effects are uncommon. Minoxidil costs about £80 for a six-month supply.
• Finasteride: this is taken in tablet form and is only available to men. It works by preventing the hormone testosterone being converted to the hormone dihydrotestosterone (DHT). About 80% of men who take finasteride see improvements. Side effects are uncommon, although about 2% of men who use it experience a loss of sex drive. Finasteride costs about £90 for a three-month pack.

Both finasteride and minoxidil normally require six to 12 months of use before any effects are seen, and the balding process will normally resume if treatment is stopped.

Other treatments for hair loss include wigs, implantation of artificial hair, hair transplants and plastic surgery procedures, such as scalp reduction.

As a general rule, it's easier to maintain existing hair than to regrow it, and once the hair follicle has stopped working it cannot be revived.

"Start by talking to your GP, who can then refer you to a specialist NHS consultant," says Dr David Fenton, a consultant dermatologist at St John's Institute of Dermatology at St Thomas' Hospital in London.