Alopecia, or hair loss, is a distressing turn of events. The scalp is often afflicted but it can occur on any part of the body.

Why does this happen? Are there different types of hair loss?

Our hair follicles perpetually cycle through a growth and resting phase. The growth phase is called anagen, the resting phase, telogen, and the time in between as the follicle shuts down for a rest, catagen.

Alopecia occurs through a disruption of either the follicle's normal cycle or by damage to the follicle itself. The evaluation of hair loss always begins with a complete medical history and physical exam.

You can assist your doctor by noting the duration and pattern of the hair loss. Are the hairs broken or shed at the roots? Has the hair loss increased recently? Do you have a family history of alopecia?

The "pull test" defines normal shedding of the hair. Grasp about 60 hairs between the thumb and index and middle fingers. Pull them gently, but hold them firmly. Six or fewer hairs left between your fingers is considered normal shedding.

The most common type of hair loss in men and women is androgenic alopecia. Each hair follicle has androgen (male hormone) receptors. Activation of these receptors by the hormone dihydrotestosterone (DHT) shortens the anagen phase. The hair follicles will shrink. With each cycle the hair becomes thinner and the follicle smaller. In women, the thinning and hair loss occurs over the entire scalp but is most pronounced at the crown of the head and areas toward the forehead.

Women with androgenic alopecia do not have greater levels of androgens. Indeed, most have normal menstrual cycles, fertility and hormonal function. What has been found is that these women have greater levels of an enzyme that converts their normal levels of testosterone into DHT, lower levels of an enzyme that converts testosterone into estrogen and more androgen receptors in the hair follicle itself. All these factors add up to more hair loss.

The medication recommended to treat androgenic alopecia in women is minoxidil (Rogaine). It works by increasing the anagen phase, activates follicles stuck in the catagen phase and enlarges the hair follicles.

One clinical trial demonstrated minimal hair regrowth in 50 per cent of women and moderate regrowth in 13 per cent. Other trials demonstrated improved hair regrowth.

Alopecia areata can appear as the sudden appearance of one- to two-centimetre-round shiny bald patches on the scalp. It occurs in two per cent of the population, equally affecting males and females. It is more common in children and young adults. The body's immune system attacks the hair follicles for unknown reasons. Some people can experience complete loss of scalp hair.

Some people with thyroid disease, eczema or vitiligo (loss of skin pigmentation) will exhibit this condition but most afflicted people are healthy.

Treatment options include local steroid injections into the bald spot, steroid creams, anthralin and minoxidil. Unfortunately, they are not completely effective. Other treatment options include several herbal hair loss remedies. However, the condition will spontaneously resolve and recur.

Emotional and physical stressors can cause sudden non- permanent hair loss called telogen effluvium. Women will notice a lot more hair on their hairbrush or shower floor. Some will experience hair loss after pregnancy or from certain medications.

Telogen effluvium occurs when a great number of hair follicles become inactivated or enter the telogen phase. The follicles will enter anagen phase one to two months after the end of the stressful event.

Traumatic alopecia is due to certain hair styling practices. Tight braiding and repeatedly twisting and tugging the hair can cause the hair to fall out.

Hair loss does not occur with frequent shampooing and conditioning. Having your hair styled, coloured, teased, sprayed or permed will not worsen hair loss.

If you suspect hair loss, consult your doctor sooner rather than later.

By Dr. Barry Dworkin, Ottawa Citizen, 04-06-2004