THE HAIR GROWTH CYCLE

We're born with all our hair follicles already in place. While some may change in size over time, we don't develop any new ones after birth. As adults, we have about 100,000 individual strands of hair. It's completely normal to lose some 40 to 100 strands every day. Normal thinning hair is the result of the growth cycle of the follicles, similar to an 'on off' system. This means that when an old hair 'dies', the growing phase starts again for a new hair to replace it. The hair growth cycle has three different phases:
 

1.  Anagen

The Anagen phase is the growing phase or the 'on' phase, which lasts for an average of approximately 1,000 days in the human scalp, but can range from 2 - 6 years. During the Anagen phase, hair cells proliferate rapidly. The hair shaft grows in diameter and the hair reaches maximum length.
 

2.  Catagen

The Catagen phase lasts only 1 - 2 weeks - it's the transitional or regressive phase before the resting phase begins. It's essentially when the hair stops growing.
 

3.  Telogen



The Telogen phase is the final resting stage or 'off' phase, which lasts for about 5 - 6 weeks.
 

When the old hair is in the Telogen phase, activity in the hair follicle is renewed. A new hair in the Anagen phase develops and forces the old Telogen hair out. This is when hairs are lost and you might notice them in the bath or in your brush or comb.
As mentioned, on average 40-100 hairs are lost due to this natural growth process every day. This is normal thinning hair and accounts for the thinning hair seen every day in the shower and with hair combing. In healthy follicles these hairs will soon be replaced by new hair.

A variety of factors can alter the normal hair growth cycle and cause temporary or permanent thinning hair including medication, radiation, chemotherapy, exposure to chemicals, hormonal and nutritional factors, thyroid disease, generalised or local skin disease, and stress.

You can read more about the causes of thinning hair in our Types of thinning hair section.

FACTS ABOUT HAIR AND THINNING HAIR

• The average person has 100,000 - 150,000 hairs on their head
• One hair fibre can support the weight of 100 grams
• The main component of hair is the keratin, which also holds the responsibility for the elasticity of the finger nails
• Hair is the second fastest growing tissue in the body (bone marrow is quicker). A hair grows 0.3-0.5mm per day
• In any given time, about 10% of the hairs are resting and the rest are growing
• Everyone loses more than 40% of his/her hairs - about 100 hairs a day
• Thinning hair will be visible only after losing more than 50% of hair
• More than 50% of men above the age of 50 suffer from thinning hair
• Between a third and two thirds of all women experience thinning hair or thinning hair at some stage in their life.
• The most common forms of thinning hair in women are Effluviums (all over thinning of hair)
• Common reasons for thinning hair include: postnatal, menopause, HRT, The Pill, stress, diet and trauma.
• Great looking hair makes you feel good - it also attracts the attention of the opposite sex.
• It is part of our personality.
• Hair gives us key information about someone’s health. Healthy hair tends to mean a healthy person.
   

MYTHS RELATED TO THINNING HAIR

The following are some common myths about thinning hair that people tend to believe. These are false!

• Frequent shampooing contributes to thinning hair.
• Hats and wigs cause thinning hair.
• 100 strokes of the hair brush daily will create healthier hair.
• Permanent thinning hair is caused by perms, colours and other cosmetic treatments.
• Shaving one's head will cause the hair to grow back thicker.

TYPES OF THINNING HAIR


Alopecia Areata

Alopecia Areata is thought to be an auto-immune disease of the hair which means that the body's immune system acts as if the hair follicles are foreign and attacks them. White blood cells called T- lymphocytes attack the hair follicle which causes the hair to stop growing and to enter into the telogen (resting) phase. About 3 months later, when the resting phase is over, the hair will then fall out. Only when T-lymphocytes stop attacking the hair follicle will new hair grow.

Alopecia Areata initially appears as a rounded bare patch about an inch across. It affects both men and women equally and is often experienced first in childhood. According to a survey taken in America, one person in every hundred is likely to experience Alopecia Areata at sometime in their life. Many people affected with Alopecia Areata will only have one experience of thinning hair with regrowth occurring afterwards, however it is estimated that in approximately 20 percent of cases, thinning hair recurs or becomes permanent.

There are three types of Alopecia Areata, which are named according to their severity. These are as follows:

Alopecia Areata: mild patchy thinning hair on the scalp
Alopecia Totalis: loss of all scalp hair
Alopecia Universalis: loss of scalp and all body hair


Self induced thinning hair

Some damage to the hair is self-inflicted sometimes consciously or unconsciously. The two main types of self-induced thinning hair are Trichotillomania and Traction Alopecia.


Trichotillomania

Trichotillomania is self-induced thinning hair, which results from the continuous pulling or plucking of the hair. It occurs most commonly among young children, adolescents and women and affects twice as many females as males. The hair is often pulled out in distinct patches on the scalp however, some individuals also pull out eyebrows and eyelashes.

The treatment for Trichotillomania often involves counselling or psychiatric help, however in some cases an antidepressant may be prescribed.


Traction Alopecia

Traction Alopecia is usually caused by continuous and excessive pulling on the hair due to various types of hairstyling. Ponytails, buns, braiding and cornrows and hair extensions often result in a continuous pulling on the hair. This traction gradually results in thinning hair. If this type of traction and thinning hair continues for an excessively long period of time then the thinning hair may become permanent. Generally however a change in hairstyle that reduces the traction on the hair and hair follicle is all that is required in the treatment of Traction Alopecia.


Androgenetic Alopecia

Androgenetic Alopecia resulting in thinning is known as Alopecia. When it is related to hormones (androgens) and genetics, it is known as Androgenetic Alopecia, or more commonly just balding. Male pattern alopecia is characterised by a receding hairline and/or thinning hair on the top of the head. A similar type of thinning hair in women, female pattern alopecia, results in thinning hair on the vertex (top) of the scalp but is generally less severe than occurs in males. The Norwood-Hamilton Scale (Fig 1.) shows the progressive stages of male pattern thinning hair. Left untreated, male pattern thinning hair is a condition that usually gets worse

Fig 1. Norwood Hamilton Scale

The Ludwig Thinning hair Scale (Fig 2.) measures the typical progression of female-pattern thinning hair.

Fig 2. The Ludwig Scale

Telogen Effluvium

Telogen Effluvium occurs when sudden or severe stress causes an increase in the shedding of the hair. With Telogen Effluvium, a sudden or stressful event can cause the hair follicles to prematurely stop growing and enter into a resting phase. The hair will then stay in the resting phase for about 3 months after which time a large amount of hair will be shed. Often the person involved will have recovered from the event before the thinning hair occurs. In most cases the thinning hair is temporary and the hair soon recovers. However in some cases the thinning hair continues until the underlying cause is fixed. Telogen Effluvium appears to affect more woman than men because more of the precipitating events (such as childbirth) are experienced by women.

Telogen Effluvium can be caused by the following:

• Hormonal changes
• Infections of the scalp
• Major surgery/chronic illness
• Severe psychological stress
• Crash diets/inadequate protein
• Drugs/medication

Hormonal changes:

There are many reasons for hormonal changes within the body; a lot of these can result in thinning hair such as:


Thinning hair after child birth:

It is quite common for some women to experience some thinning hair approximately 3 months after childbirth. This thinning hair is triggered by the sudden changes in hormone levels.

Some statistics suggest that 20 percent of mothers lose hair after childbirth and others suggest a figure closer to 45 percent. Fortunately, in most cases the hair will return to normal 9-12 months after childbirth.

Many women notice that their hair is thicker and healthier during pregnancy, this is due to the increased levels of hormones oestrogen and progesterone, which cause more hairs than normal to remain in the growth phase. When the child is born however, many of the hair follicles that had delayed entering the resting phase suddenly enter the resting phase due to a rapid drop in hormone levels. As a result, these hairs are then shed about 3 months after the birth.


Thinning hair resulting from taking the birth control pill:

Birth control pills affect the hormone levels within the body and these hormone levels can affect hair growth. In some cases, hair thinning may occur due to the male hormones present in some contraceptive pills. This type of thinning hair is similar to pattern baldness or Androgenetic Alopecia. However, discontinuation of the pill can result in thinning hair similar to that which occurs after childbirth due to the drop in hormone levels.


Thinning hair resulting from thyroid gland malfunction:

Generally the first test a doctor or specialist is likely to carry out on a patient who is experiencing thinning hair is a thyroid function test, as a thyroid problem may result in thinning hair. Two types of thyroid problems can occur and either of these problems can result in thinning hair. These conditions are hypothyroidism (the under production of thyroxine) and hyperthyroidism (the over production of thyroxine).

Thinning hair may occur from either hypothyroidism or hyperthyroidism. In some cases thinning hair is minimal, however some individuals experience severe thinning hair. Fortunately thinning hair is usually reversible with proper treatment. If you suspect that you have a problem with your thyroid function then you should visit your doctor.


Infections of the scalp:

Infections such as ringworm can invade the hair and skin of your scalp, leading to thinning hair. Once infections are treated, hair generally regrows.


Major surgery/chronic illness:

The shock involved in a major operation can result in sudden thinning hair. Also after micro graft and mini graft surgery where follicles are transplanted on the scalp Telogen Effluvium almost always occurs. Due to the shock of surgery the hair follicles will fall out within about 3 months after which time new hairs will grow from the transplanted follicles.

Some cancer treatments will cause hair cells to stop dividing. Hairs become thin and break off as they exit the scalp. This occurs one to three weeks after the treatment. The hair will regrow after treatment ends.


Severe physiological stress:

Some people experience Telogen Effluvium or sudden diffuse thinning hair after a traumatic event such as the death of a family member or someone close, an accident, abuse or any other severely traumatic event. These events may trigger hair follicles to enter the resting phase prematurely in which case an increase in the amount of hair shed will be noticed about 3 months after the event. When the stressful situation is over or the body adjusts to it, the hair usually grows back.


Crash diets/inadequate protein:

Some people who go on crash diets that are low in protein, or have severely abnormal eating habits, may develop protein malnutrition. The body will save protein by shifting growing hairs into the resting phase. Massive hair shedding can occur two to three months later. Hair can then be pulled out by the roots fairly easily. This condition can be reversed and prevented by eating the proper amount of protein and, when dieting, maintaining adequate protein intake.


Drugs/medication:
Some prescription drugs may cause temporary hair shedding. Examples include some of the medicines used for the following: gout, arthritis, depression, heart problems, high blood pressure, or blood thinning. High doses of vitamin A may also cause hair shedding.

The following is list of some drugs that have been reported to have a side effect of thinning hair:

• Alloppurinol (for the treatment of gout)
• Heparin (blood thinner)
• Coumarin (blood thinner)
• Clofibrate (cholesterol lowering drug)
• Gemfibrozil (cholesterol lowering drug)

The above drugs are only a few of the drugs that have been reported as contributing towards thinning hair. If you suspect that prescription drugs that you are taking are causing thinning hair you should discuss this with your doctor.