Genes determine the shape of our hair, its colour, thickness and density and how fast or long it grows. The genes that control these characteristics are inherited from each parent.
Genes also determine whether you are going to be susceptible to male pattern baldness (androgenetic alopecia) or not.
There are also some congenital types of baldness (that is, baldness present from birth) and structural abnormalities of the hair which are inherited.
Some races are more prone than others to develop male pattern baldness. Caucasians are particularly prone and may develop very severe forms of male pattern baldness; Blacks are less prone and Orientals the least prone.
Hair grows faster in women than men-a good excuse for women if their menfolk complain of their frequent visits to the hairdresser! Women also have more problems with hair breakage because of damage from bleaching, permanent waving and styling. However, women are protected by female hormones and tend to have less severe male pattern baldness.
Androgens, the male hormones present in both men and women, are believed to be the main cause of male pattern baldness in a genetically predisposed person. Fig. 4 shows the sites of androgen production in men and women.
Oestrogen, female hormones produced by the ovaries, counteracts the effects of androgens (Fig. 5). This is why women tend to have less severe male pattern baldness than men. The only exception is in women who produce excess androgens. These women not only have severe male pattern baldness, but also hirsutism (excessive and coarse facial hair), severe acne, menstrual disturbances and infertility.
Androgens are necessary in order for male pattern baldness to develop. If androgen production is cut off by castration, males will not develop male pattern baldness at all. However, given the choice of a good sex life or baldness, I have no doubt which men would chose!
Other hormones may also affect hair. Lack of the pituitary hormones or too much or too little thyroid hormones can cause diffuse thinning of the hair. A transient deficiency of thyroid hormones may also contribute to the hair loss that occurs after pregnancy (see next section).
Pregnancy and childbirth
The increase in nutrition and hormones necessary to support pregnancy also affects the hair. During pregnancy, anagen (growing stage) is maintained for longer than normal and about 95% of the hairs are in anagen. After delivery, nutrition and hormone levels return to normal and the hair becomes somewhat starved. This causes the hair to go into telogen (resting stage).
Since more hair was in anagen to begin with, more will also move into telogen. These telogen hairs are shed at the end of telogen, two to five months later. This condition is known as telogen effluvium. Telogen effluvium after pregnancy is self-limiting and hair grows to its normal state after six months or so.
Another cause of hair loss after pregnancy is hypothyroidism (lack of thyroid hormones). This is known to cause diffuse thinning of the hair. About 10% of pregnant women develop a transient thyroid deficient state after delivery and this may account for some of the hair loss. However, thyroid levels return to normal after six months and so does the hair.
Iron requirements increase during pregnancy and iron deficiency may develop if dietary intake is insufficient. This may also cause a diffuse thinning of the hair. However, iron deficiency during pregnancy is uncommon because most women take iron supplements during pregnancy or take enough iron in their diet.
Birth control pills
The most popular birth control pills are the combined pills which contain an oestrogen and a progestogen (a synthetic progesterone). Oestrogen and progesterone are female hormones.
Birth control pills prevents pregnancy by making the body believe it is pregnant. The effect of this on hair is more or less the same as in a true pregnancy, that is, anagen is prolonged. When you stop taking the pills, large quantities of anagen hairs are pushed into telogen and this is followed by a telogen effluvium two to five months later.
A second form of hair loss can also occur. The combined pill can be classified into oestrogen-dominant and androgendominant pills. Androgen-dominant pills contain progestogens which have androgenic properties. Women taking these pills may sometimes develop male pattern baldness if they happen to be genetically predisposed. Check with the pharmacist or your doctor if you are not sure.
The ovaries that produce female hormones become inactive after menopause and the protection of oestrogens is lost. Androgens are not affected because they are still produced by the adrenal glands which sit on top of the kidneys. The unopposed action of androgens cause many women to develop male pattern baldness after menopause.
The number of hair follicles and hair falls with age from puberty onwards. When a person is 20-30 years old, there are about 615 follicles per square centimeter on his scalp. By the ages of 30-50 years, this falls to 485. By 80-90 years, it becomes 435 per square centimeter. Thinning of the hair, therefore, occurs as part of the ageing process.
Insufficient intake of iron in the diet may cause diffuse thinning of the hair. The iron in vegetables is inferior compared to that in meat and strict vegetarians may suffer from iron deficiency.
Iron deficiency may also develop during pregnancy if intake is insufficient (see pregnancy and childbirth). Chronic blood loss from any cause, like bleeding ulcers, haemorrhoids (piles) and heavy periods may also lead to iron deficiency. This can be detected through a blood test.
Protein malnutrition may cause alterations in hair colour and texture, and increased hair loss. However, this is uncommon in countries with high standards of living. The more likely cause of diet-related hair loss in these countries is not malnutrition but self-imposed crash diets.
Self-imposed starvation deprives the hairs of essential nutrients and cause them to go into telogen (resting stage). This is followed by telogen effluvium two to five months later.
Sudden, severe emotional stress can precipitate telogen effluvium or alopecia areata, but it is not clear whether chronic stress can also aggravate an existing hair loss problem.
But why take chances? Reducing stress will certainly not make hair loss worse and may even help. Moreover, stress can cause other problems such as tension headaches, digestive problems, stomach ulcers and heart attacks. Reducing stress is undoubtedly a good thing.
Stress may affect hair in another way. Some people have a habit of twirling or biting their hair. This can cause hair loss or breakage.
Trichotillomania, a compulsive hair-pulling disorder that usually affects children and women, is also due to underlying emotional stress (Fig. 6). Maria, the girl mentioned earlier, suffered from this condition (p. 8).
On the other hand, there are some people who complain of "hair loss" but show no evidence of it, or at least no greater thinning than their contemporaries. These individuals may suffer from a disturbance of body image.
This condition, known medically as dysmorphophobia, was described by English dematologist Dr John A. Cotterrill. He described it to be a symptom of underlying psychiatric diseases such as depression, which require treatment.
Friction from tight hair bands, wigs and hats can sometimes cause hair to break. In infants, hair loss may occur as a rim along the back of the head due to friction from the pillow case or crib sheet before the baby is able to lift its head. The hairs are telogen hairs which are destined to be shed. The hair loss is, therefore, harmless and temporary.
Prolonged pressure on one area of the scalp during long medical operations that exceed four hours may cause alopecia. Redness, oozing and cru_ing appears several days after the operation, and this is followed by hair loss the next month. It is due to reduced blood flow to the hair follicles in the region. This is temporary.
Improper and over vigorous scalp massage may cause hair to break, adding another problem to hair loss.
Permanent waves, frequent bleaching, the use of hot combs and hair straighteners may damage the hair and cause breakage. Com-rowing, tight braiding, buns, tight curlers and ponytails can also pull hair out by the roots and cause a type of alopecia known as traction alopecia. This characteristically affects the front and temples.
Ringworm of the scalp (tinea caPitis) typically produces red scaly balq patches with broken-off hair stumps (Fig. 7). Children are more commonly affected.
A very severe form of tinea capitis may be caused by animal fungi. It results in a large, painful abscess called a kerion. Kerions may cause severe scarring and permanent hair loss. Fungal infections can be confirmed by microscopic examination and culture (growth) of specimens of hair. The treatment is with oral and applied anti-fungal medication.
Bacterial folliculitis (an infection of the hair follicles) may also cause hair loss. If severe, scarring and permanent baldness may result; early treatment with oral antibiotics helps prevent this.
Secondary syphilis may cause a patchy "moth-eaten" type of alopecia. The diagnosis can be confirmed with the Venereal Disease Reference Laboratory (or VDRL) blood test. Hair re-grows after treatment.
Prolonged fever caused by infections such as malaria and typhoid can also cause telogen effluvium.
A number of drugs have been reported to cause hair loss. These include blood-thinning drugs such as warfarin, heparin and phenindionej anti-thyroid drugs such as thiouracil and carbimazolej and anti-cancer drugs such as cyclophosphamide, adriamycin and vincristine.
Excessive intake of vitamin A also causes hair loss. Roaccutane (13 cis-retinoic acid), a vitamin-A derivative used for the treatment of severe acne, can also cause hair loss which is reversible when intake is stopped. Birth control 'pills are another cause of drug-induced hair loss.
Skin diseases such as discoid lupus erythematosus, lichen planus and scleroderma may affect the scalp and cause scarring and permanent hair loss.
These conditions can be confirmed with a scalp biopsy (see page 82). Early treatment is necessary because scarring can completely destroy the hair follicles, eliminating all chances of re-growth.
Underlying cancers, particularly Hodgkin's lymphoma (a cancer of the lymph glands), are another rare cause of diffuse hair loss.