What is 'male pattern' baldness?

• Trichologists (specially trained hair specialists) grade the extent of hair loss using the "Hamilton Scale". This describes a series of stages, ranging from a slight receding at the front hairline (Stage I) to the development of a large bald spot on the crown combined with a marked receding at the front (Stage VII). Men who reach this final stage typically have just a horseshoe-shaped fringe of hair above the ears. In male pattern baldness, complete loss of hair is rare.
• It's not just the pattern of hair on the scalp that changes in male pattern baldness – the quality of hair is affected too. Each hair on your head goes through a distinct cycle of growth, rest and shedding, after which it is replaced by a new hair growing from the same follicle on the scalp. But in male pattern baldness, each time a hair is shed its replacement becomes progressively thinner, because the hair follicles themselves shrink – making the diameters of the hairs they produce smaller.
• This inevitably results in decreased coverage of the scalp. When a hair follicle shrinks so much that it stops producing hair altogether, the corresponding area of scalp becomes devoid of hair (i.e. bald), while the rest of the hair just becomes thinner and finer.
• What's more, the hair also spends less time in the growth phase of its cycle, which means that new hairs also become progressively shorter. Again, this results in reduced coverage of the scalp.