Hair loss

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VOL 113 / NO 1 / JANUARY 2003 / POSTGRADUATE MEDICINE

You are worried by the increasing number of hairs that you find in your hairbrush each day. Will your hair ever stop falling out like this? Why is this happening, and is there anything you can do to stop it?

What is hair loss?
On average, each person has 1 million hair follicles, or sacs from which hair may grow, on the scalp. Of this number, only 100,000 to 150,000 have hair growing from them. At any one time 80% to 90% of these follicles are growing hair; the remainder are "resting." With age, more follicles begin to rest. Normally, 100 to 150 hairs fall out each day; this number increases each fall and decreases each spring. Occasionally, more hairs fall out than normal--sometimes in clumps--leaving areas of thin hair or baldness. This condition is called alopecia (al-o-PEA-she-ah).

What causes hair loss?
Most hair loss results from changes in the levels of hormones, a group of chemicals naturally produced by the body. This occurs even though the measured levels of hormones remain within the normal range; people who experience this type of hair loss appear to be especially sensitive to these changes in hormone levels.

People whose parents have experienced hair loss are more likely to have it, too. A condition called androgenetic alopecia occurs in some men, who begin to lose hair at the top or front of the head starting between ages 20 and 40. This type of alopecia eventually also affects at least one in four women, who lose some or a lot of hair all over their head.

Various diseases and other conditions can cause hair follicles to go into the resting stage, resulting in bald patches. Severe or prolonged illness, starvation, anorexia nervosa, rapid weight loss, infection, injury, and excessive blood loss can all cause hair to fall out. Many women experience hair loss after childbirth, a miscarriage, or a change in their birth control pill prescription. Certain drugs, such as amphetamines, anticancer agents, gout medication, isotretinoin (Accutane), lithium, male hormones, propranolol hydrochloride (Inderal), and valproic acid (Depacon, Depakene, Depakote), also can cause hair loss.

About 1 in 100 people experience a condition called alopecia areata during their lifetime. This type of hair loss usually occurs quickly and results in one or several oval or circular areas of baldness. The cause is unclear, although this disease has been known to occur in persons who have such diseases as lupus erythematosus, thyroiditis, or vitiligo. Hair usually regrows in these bald spots, but it may not regrow if the disease is severe, also affects the nails, occurs in children, or lasts longer than 5 years. Infection with ringworm, certain bacteria, herpes zoster (shingles), and HIV also has been blamed for hair loss, as have syphilis and AIDS.

A lack of iron in the body may lead to hair loss, particularly in young and middle-aged women. In rare cases, a lack of zinc may be to blame. Conditions such as uncontrolled diabetes, hypothyroidism or hyperthyroidism, or use of the hormone testosterone in postmenopausal women may also cause hair loss.

Poor hair care, such as use of hot combs or very tight braiding, as well as scarring from cosmetic surgery, may result in hair loss.

How long will hair loss last?
Hair loss usually begins 6 to 16 weeks after the start of the illness, condition, or therapy that caused it. In most instances, it stops after several months, except when androgenetic alopecia is involved. Total hair loss is rare except in the case of anticancer drugs, although the hair usually grows back after treatment ends.

How can I stop hair loss?
Many cases of hair loss get better on their own over time. Others may respond slowly to treatment. However, any hair that grows back may be thinner than the hair you had originally. It is a good idea to doubt advertising claims about so-called cures using vitamins, herbs, or nutritional supplements; none of these treatments have been proven to work for hair loss.

For men with androgenetic alopecia, physicians may prescribe the drug finasteride (Propecia) to be taken by mouth or recommend the over-the-counter drug minoxidil (Minoxidil for Men, Rogaine) to be applied to the scalp. Women may be given minoxidil or a hormonal or iron supplement. If the hair loss is caused by an infection, an antifungal or antibacterial medication can be helpful. Alopecia areata sometimes responds to use of a steroid drug.

This information is not a substitute for medical treatment.

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