Derrick Garwood, Freelance Medical Writer and Editor

Hair loss or alopecia in men is widely regarded as a suitable topic for one-liners such as "I knew I was going bald when it took longer and longer to wash my face". This is hardly surprising considering the effort and ingenuity that goes into disguising follicular shortcomings. For example, in 1975 the American Patents Office registered a special way of combing hair for bald people! It is all to do with layering and hairspray, apparently. However, seeing handfuls of hair gather conspiratorially in the plughole after shampooing can be a very traumatic experience, which also affects women.

Scalp hair grows at a rate of about 1 centimetre per month for two to six years (the anagen phase), before entering a resting or telogen phase that lasts two or three months, and then falling out. At any given time, some 90% of the hair is actively growing. This page gives a very brief account of the major causes of excessive hair loss, including genetic predisposition, illness, hormonal changes, infection, medication, and improper hair care.

Genetic, or androgenic, alopecia is the most common cause of hair loss; it may begin as early as 20 in men, with two thirds of Caucasian males becoming noticeably bald before 40, while 30% of Caucasian females are affected before the menopause. This photograph shows typical male pattern baldness; the hair starts receding at the temples to give an 'M-shaped' hairline, whilst simultaneously thinning at the crown. Eventually the two depleted areas meet and coalesce, leaving just a horseshoe-shape of hair around the sides of the head. Female pattern baldness, as here, comprises a general thinning of hair all over the head, sometimes with a moderate loss at the hairline.

The causes of androgenic baldness are complex and incompletely understood, but involve both hormonal and genetic factors. The reaction of the hair follicles to testosterone and its more potent derivative dihydrotestosterone (DHT) plays an important role, but the speed, pattern, time of onset and degree of balding are all influenced by heredity. This site also includes information about the prescription medications minoxidil and finasteride, which have been shown to slow the rate of hair loss and stimulate new hair growth in some patients with this type of alopecia.

Physiological stresses such as febrile illness, major surgery, hormonal changes, pregnancy, anorexia and medication can cause a large number of hairs to simultaneously switch from the anagen phase to the telogen phase. Approximately three months after the precipitating event these hairs are shed; this form of alopecia is termed telogen effluvium. Body hair is not usually affected – hair is lost diffusely from the entire scalp but complete alopecia is not seen. In both this photograph and in this one you can see diffuse thinning over the entire scalp with a pronounced widening of the parting. Providing any underlying causes are corrected, the condition is totally reversible, usually within about 6 months.

During the anagen phase, the matrix cells of the hair follicle undergo vigorous mitotic activity. Radiotherapy and chemotherapeutic agents used to treat cancer have a profound impact on cell division in these cells, leading to a weakened hair shaft susceptible to fracture, or even to a complete failure of hair formation. This is anagen effluvium. Diffuse hair loss usually begins 7 – 14 days after exposure to chemotherapy, but is most apparent after 1 – 2 months, and can be quite extensive, as here. Again the condition is completely reversible, but the new growth may differ from the original hair in colour and texture. At the bottom if this page there is a good section on differentiating anagen effluvium from telogen effluvium.

It is quite common to see people with a few small, bare patches of scalp, although not generally as extensive as this. These are the result of alopecia areata, an autoimmune condition in which the white blood cells attack hair follicles. On rare occasions it progresses to produce a total loss of head hair or even the loss of all head, face and body hair. The cause is unknown, but it is thought that a genetic predisposition is triggered by a viral infection or environmental factor. The course of the disease is unpredictable; some people lose a few patches of hair, which later grows back, and the condition never recurs. In others the hair never re-grows, or there is continual loss and re-growth, and sometimes the new growth is white, gradually assuming the colour and texture of the original. Research is focused on areas such as gene-mapping, new therapeutic agents, drug delivery and understanding stem cell biology.

Placing excessive tensional forces on hair shafts, as a result of styling practices such as braiding or pigtails, can lead to focal hair loss. This is traction alopecia and the area affected depends on the way the hair is being pulled. If the condition is ignored, scarring and permanent hair loss may result over much of the scalp.

Various surgical techniques are available to replace hair when re-growth is not possible, including transplantation, flap repositioning, tissue expansion and scalp reduction. These are explained on this plastic surgery site, complete with diagrams, and prospective patients are warned that follow-up procedures are often required to improve the aesthetic result. To get a better appreciation of transplantation have a look at the animations and videos of two procedures (follicular unit strip excision and follicular unit extraction) here. For men, however, perhaps the best solution is simply to shave off what little hair remains – it is much cheaper, and the totally bald pate is currently deemed the epitome of cool.........but for how long?

This tour was submitted by Derrick Garwood, a Freelance Medical Writer and Editor, please feel free to email Derrick

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