Facts About Hair Loss

 
Everyone experiences some hair loss.  This is because hair is shed naturally as part of the normal hair life cycle.  As each new hair prepares to grow out from the hair follicle, the old hair is pushed out and shed.  Other types of shedding--sudden or excessive shedding--are caused by a host of factors, including disease, radiation damage, certain medications, and so on.
Androgens, or male hormones, have a major influence in regulating hair growth. As far back as 400 BC, Hippocrates observed that eunuchs did not become bald, indicating that a male-specific factor was involved in hair loss. Women tend to have less extensive hair loss (also called thinning hair) than men, because women produce lower amounts of androgens which are the primary sex hormones produced in the testes.
Some of the conditions that cause hair loss include:   - alopecia areata   - androgenic alopecia   - telogen effluvium   - trichotillomania and traction alopecia
Thinning of the hair, or alopecia, occurs in approximately 30-40% of adults, in both men and women.  Some causes of alopecia are correctable by treating the underlying problem or by discontinuing the offending agent--such as radiation damage. Causes of alopecia include: thyroid disease, inadequate protein intake, ingestion of certain medications (such as oral contraceptives), cancer chemotherapy, iron deficiency, fungal infections, and improper hair care.
Other causes of thinning hair are generally self-limiting.  Causes that are self-limiting include childbirth, high fever, a severe infection, or major surgery.  However, alopecia that accompanies chronic illness may persist indefinitely.
Certain styling techniques can also cause hair damage, hair loss, and hair-follicle damage.  These styling techniques include the excessive pulling (traction alopecia) on hair, such as from straightening curly hair.  These damaging techniques also include waxes and hot combs, which harm both hair and hair follicles.  Damaged hair follicles may shrink, atrophy, or may die completely.  Damaged hair follicles may not be able to regrow hair even after the styling techniques are no longer used.
Androgenetic alopecia
Androgenetic alopecia accounts for 95% of all hair loss.  While a person normally sheds 50 to 100 scalp hairs per day, in androgenetic alopecia the rate of hair shedding increases.  In women, this condition appears as diffuse hair loss over the entire scalp.  In men, the pattern usually starts with a receding hairline, then advances to the top of the head. By the age of 60, two thirds of men will suffer hairloss. This represents some 40 million men in the U.S.. In the U.S. 20 million women are estimated to suffer from hairloss.
The excessive shedding seen with this condition is caused by a shortened growth phase in the hair's life cycle.  Scalp and other tissues contain an enzyme called 5-alpha reductase.  This enzyme causes a potent male hormone (dihydrotestosterone, or DHT) to be formed in the hair follicle.  However, in androgenetic alopecia, genetically primed follicles overproduce the hormone.  This shortens the active growth portion of the hair life cycle. Eventually, the shortened life cycle leads to degradation of the follicle. The follicle may die or simply shrink to a size that produces only a fine, unpigmented (vellus) hair. At a certain point, the hair is too thin and fragile to survive, and baldness occurs.
Treatment of Androgenetic Alopecia
Currently there are two FDA approved treatments for androgenetic alopecia:  minoxidil and finasteride. Both minoxidil and finasteride require living hair follicles in order to work.  This means that a dormant or atrophied hair follicle can still be stimulated back into a growth phase.  A hair follicle that is dead cannot be reestablished; hair regrowth will not occur from dead follicles.
Minoxidil
Minoxidil is the most widely recommended treatment, and is available as a generic, over-the-counter (OTC) medication. It was originally used to treat high blood pressure, but the drug was also found to stimulate hair growth.  Now, minoxidil can be used in topical form for alopecia treatment.
Minoxidil appears to work by gradually enlarging and lengthening hair follicles that have been shrinking due to the action of excessive amounts of the hormone dhydrotestosterone, or DHT. Minoxidil may also extend the growth phase of the hair follicle.
Minoxidil must be used on a continual basis. Generally the drug must be used for 3 to 4 months before there is obvious hair regrowth in those individuals who will respond to the drug.  Initially, new hair may be soft and colorless, but eventually it will attain its normal appearance.
The most common side effects of minoxidil are itching of the scalp and skin irritation.  In general, these side effects disappear when treatment is discontinued.
Clinical tests on minoxidil have been conducted by 27 US medical centers involving over 2,300 patients.  The tests have been conducted on both a 2% minoxidil formulation and a 5% formulation. The tests indicated that after 1 year of 2% minoxidil use, 48% of the men had moderate to dense hair regrowth, and another 36% of the men had minimal hair regrowth. Two thirds of the women had some degree of hair regrowth.  Use of the new 5% formulation appears to result in an additional 45% increase in hair growth when compared to the 2% formulation.
Finasteride
Finasteride is an oral prescription medication.  It is approved for use only in men. It is not recommended for use in women because of its high potential for causing birth defects.
Finasteride is an inhibitor of the enzyme called 5-alpha reductase. This enzyme causes the male hormone dihydrotestosterone (DHT) to be formed in the hair follicle.  By inhibiting 5-alpha reductase, finasteride decreases DHT synthesis.  Reducing the amount of DHT that can be synthesized thus reduces the destructive effects of excessive amounts of DHT on the hair follicle.
Treatment with finasteride must occur for at least 3 months before regrowth begins to be apparent.  After that, therapy must continue in order to maintain those effects. Approximately 83% of users have hair regrowth after 2 years.  Two side effects are seen in 2% of finasteride users:  impotence and loss of libido.
Alopecia areata
Alopecia areata affects about 1.7% of the US population. This condition is seen in both men and women, and is often first seen in childhood.  There are three types of alopecia areata that affect extensive areas of skin:  - Alopecia areata is mild, patchy hair loss on the scalp, and may also affect the growth of hair at other body sites.  - Alopecia totalis is the loss of all scalp hair.  - Alopecia universalis is the loss of scalp and all body hair.
Alopecia areata is thought to be caused by an inflammatory response.  This inflammatory response is caused by the body's immune system erroneously attacking hair follicles.  The attack on the hair follicles causes the hair to enter a resting phase, which is followed by a shedding phase.  New hair will not grow until the immune cells cease attacking the follicle. Approximately 20 to 30% of people with alopecia areata have a family history for this condition.
Alopecia areata is self-limiting (will halt on its own) in more than 80% of the cases.  In particular, the condition is usually self- limiting when the hair loss occurs after puberty. Hair growth may begin immediately after hair loss, or it may begin again several months to years after the initial manifestation of hair loss.
The more extensive the condition, the less likely that there will be improvement without therapy.
Treatment of alopecia areata
Treatment for alopecia areata is determined by the extent of hair loss, which is established by your physician. There are four main types of therapy:
-Topical or locally injected corticosteroids, usually used when there is less than 50% hair loss.  Corticosteriods have a multitude of effects that lead to suppression of the inflammatory response. Topical minoxidil may also be effective in individuals with patchy alopecia areata.
 - Oral corticosteroids, which may be used when there is greater than 50% hair loss
 - PUVA treatment--infrequently used.  PUVA therapy involves ingesting a light-sensitive drug, followed by short exposure to UVA light.
 - Immunosuppressive therapy, such as cyclosporine. Immunosuppressive therapy is reserved for the more severe forms of alopecia areata, and it requires close supervision by your physician.  
Telogen effluvium
Hair growth occurs in cycles, and each hair's cycle is independent of other hairs' growth cycles.  This means that individual hairs may be in different stages of life--one hair might be in a growth phase, another in a shedding phase, and other in a resting phase.
Life events can alter hair growth and cause many follicles enter the resting phase simultaneously.  A moult or significant shedding will follow such a coordinated resting phase.  Such a sudden and shedding of hair may be alarming.  Common life-event triggers for moults include childbirth, poor nutrition, some medications, cessation of oral contraceptives, severe illnesses, hemorrhage, surgery, and extreme stress.
Telogen effluvium usually resolves itself over time, without intervention by medication or other therapy.  However, scalp-hair density may never return to previous levels.
Trichotillomania & Traction Alopecia (Abnormal Pulling or Twisting of Hair)
These conditions are caused by abnormal pulling or twisting of the hair causing breakage of the hair shaft. In these conditions, the scalp is normal (undamaged).  When pulling and twisting are stopped, the hair regrows normally unless the follicle has been damaged.
These conditions in children are usually caused by a nervous habit of playing with the hair.  Traction alopecia can also be caused by certain styling techniques that pull excessively on the hair, such as straightening techniques.

What Causes Hair Loss?
What is the normal cycle of hair growth and loss?
At any one time, about 10 percent of the hair on your scalp is in a resting phase. After 2 to 3 months, the resting hair falls out and new hair starts to grow in its place. This growing phase lasts for 2 to 6 years. Each hair grows approximately 1 centimeter per month during this phase. About 90 percent of the hair on your scalp is growing at any one time.
It is normal to shed some hair each day as part of this cycle. However, some people may experience excessive (more than normal) hair loss.
What causes excessive hair loss?
A number of things can cause excessive hair loss. For example, about 3 or 4 months after an illness or a major surgery, you may suddenly lose a large amount of hair. This hair loss is related to the stress of the illness and is temporary. 
Hormonal problems may cause hair loss. If your thyroid gland is overactive or underactive, your hair may fall out. This hair loss usually can be helped by treatment of the thyroid disease. Hair loss may occur if male or female hormones, known as androgens and estrogens, are out of balance. Correcting the hormone imbalance may stop your hair loss.
Many women notice hair loss about 3 months after they've had a baby. This loss is also related to hormones. During pregnancy, high levels of certain hormones cause the body to keep hair that would normally fall out. When the hormones return to pre-pregnancy levels, that hair falls out and the normal cycle of growth and loss starts again. 
Some medicines can cause hair loss. This type of hair loss improves when you stop taking the medicine. Medicines that can cause hair loss include blood thinners (also called anticoagulants), medicines used for gout, medicines used in chemotherapy to treat cancer, vitamin A (if too much is taken), birth control pills and antidepressants.
Certain infections can cause hair loss. Children may have hair loss caused by a fungal infection of the scalp. The infection is easily treated with antifungal medicines.
Finally, hair loss may occur as part of an underlying disease, such as lupus or diabetes. Since hair loss may be an early sign of a disease, it is important to find the cause so that it can be treated.
Can improper care of my hair cause hair loss?
Yes. If you wear pigtails or cornrows or use tight hair rollers, the pull on your hair can cause a type of hair loss called traction alopecia. If the pulling is stopped before scarring of the scalp develops, your hair will grow back normally. However, scarring can cause permanent hair loss. Hot oil hair treatments or chemicals used in permanents may cause inflammation (swelling) of the hair follicle, which can result in scarring and hair loss.
What is common baldness?
The term "common baldness" usually means male-pattern baldness. Male-pattern baldness is the most common cause of hair loss in men. Men who have this type of hair loss usually have inherited the trait. Men who start losing their hair at an early age tend to develop more extensive baldness. In male-pattern baldness, hair loss typically results in a receding hair line and baldness on the top of the head.
Women may develop female-pattern baldness. In this form of hair loss, the hair becomes thin over the entire scalp.