Hair Loss and Baldness
The normal human scalp contains an average of 100,000 to 150,000 hair roots, from which individual hairs grow; the follicles are nourished by blood vessels at their base.
The life-cycle of an individual hair consists of two stages:
- a Growth stage which lasts for an average of four to five years during which, as the name suggests, the hair will grow to its full length (fashion and hairdressers willing!).
- a Rest stage, which lasts for two to four months after which the hair falls out naturally and is replaced by new hair
In general, about 90 per cent of scalp hairs are in the Growth stage and the remaining 10 per cent are in the Rest stage waiting to fall out and be replaced by new growth. Some hair loss is a normal part of the hair life cycle.
Baldness occurs when hair is lost more quickly than usual (more than the 50 to 150 scalp hairs normally lost per day), when hair is replaced more slowly than usual or when normal hair is replaced by a thinner, shorter growth.
Causes of Hair Loss
There are several conditions which can cause baldness. The underlying causes are not always well understood but are thought to involve individual genetic components, auto-immune disorders and stress.
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Androgenetic Alopecia
Androgenetic Alopecia or Male Pattern Baldness, as it is commonly known, is the cause of approximately 95 per cent of all cases of male hair loss; it affects approximately two-thirds of all men by the age of 60, with about 25 per cent of men beginning to suffer hair loss by the age of 30.
Baldness normally begins at the temples and the crown resulting in a receding hairline and a bald spot. Loss of hair may then continue until the two areas join, leaving a horseshoe-shaped area of hair on the back and sides of the head - the characteristic pattern which gives the condition its common name.
Male Pattern Baldness is thought to involve both individual hormonal and inherited genetic factors. Several hormones are involved in the growth of scalp hair - the most important being androgens.
Testosterone and dihydrotestosterone (DHT) are responsible for the development of hair follicles, during puberty, in areas such as the beard and arm pits.
However, they can also cause scalp hair follicles to reduce in size as the man ages. These very different effects of DHT may be the result of genetic differences in the individual hair follicles.
Such genetic variations in scalp hair follicles may cause the follicles to shrink in the presence of androgens. As the hair follicles reduce in size, the hair strand thins and becomes shorter.
At the same time, the Growth stage becomes shorter so that the life-cycle repeats more frequently and so more hairs are lost. Eventaully, at least some of the follicles will die.
However, recent medical advances have produced medications which can slow the rate of hair loss and can, in some cases, reverse it.
Alopecia Areata
Alopecia Areata is charaacterised by localised patches of hair loss on the scalp or any other part of the body but in rare cases it may affect the complete scalp (see Alopecia Totalis below).
This form of alopecia is thought to be a result of an auto-immune attack on the hair follicles triggered by stress.
Affected patches may not re-grow for 12 months and may grow back with a different pigmentation - often white.
Some 10% of affected people will not re-grow hair - particularly if alopecia areata is a family trait or the individual is suffering from an autoimmune disorder.
Alopecia Totalis
Alopecia totalis involves the complete loss hair on the scalp and affects both men and women. The underlying cause is not clear but it may be triggered by an auto-immune disorder or stress.
Alopecia Universalis
Alopecia universalis is the inbility of an individual to grow any body or scalp hair and can affect poeple of all ages.
Again, the underlying cause is not clear but it may be triggered by an auto-immune disorder. Alopecia universalis seems to affect fewer than 1 person out of every 100,000.
Traction Alopecia
Traction alopecia describes the effects of continued, excessive strain on hair shafts - literally, pulling ones hair out - and can lead
to permanent damage to the hair follicles, with the hair refusing to re-grow. It can be associated with specific hair styles such as braiding.
Telogen Effluvium
Telogen effluvium describes a thinning of the hair on the scalp. Again, the cause of telogen effluvium is not well understood but it is
thought to be a natural temporary state which occurs when more hairs are in the Rest / shedding stage of the life-cycle than are in the Growth stage and the hair will usually re-grow.
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