The growth cycle of hair consists of three phases:

Anagen – the active growth period

Catagen – short recession period

Telogen – resting period.

Hair that reaches the end of its life is shed and healthy new hair grows in its place.

Within this growth cycle, daily loss of about 100 hairs is considered normal.

Men

Men typically suffer from hereditary hair loss

male pattern baldness or androgenetic alopecia.

The first signs of this genetic predisposition appear after puberty between 20 and 30 years. First, the hair pulls back along the end line, then the flow of history with ever thinning hair away at the crown. In some men, this can expand all over the head. However, many keep their hair at the temples and at the nape.

The interaction of different factors

In androgenetic alopecia accordingly three factors play an important role:

Age of person

If a person has a genetic predisposition to lose hair, this will generally result in slowing the regrowth of hair.  In both women and men the production of endogenous growth factors such as IGF-1 (insulin-like growth factor), KGF (keratinocyte growth factor) and VEGF (vascular endothelial growth factor) decreases as they grow older and hair that has fallen out does not grow back due to lack of growth stimulation.

Hormones

Hormones affect the length of the hair cycle and the division activity of the hair follicles.

As early as 20 years of age, the production of growth hormone HGH (human growth hormone) decreases. Every ten years this reduces further by 14% and this affects hair regrowth.

The enzyme 5-alpha-reductase

The male sex hormone testosterone is converted by the enzyme 5-alpha-reductase into dihydrotestosterone (DHT).  DHT damages and weakens the hair roots. The enzyme 5-alpha-reductase exists in two types:

• as 5-alpha-reductase I (5aR1) in the front part of the scalp

• as 5-alpha-reductase II (5AR2) in the entire scalp

In people with an inherited hypersensitivity to DHT, the phase of hair growth (anagen) is shortened and results in a decrease in the length of hair. A bald man does not fewer hair follicles as a man with full hair growth, but because of the shortened growth phase the hair is barely visible. The scalp at the back and in the neck area is less sensitive to DHT generally.

Hair loss due to unbalanced and inadequate nutrition

Iron, zinc, sulfur and the vitamin B group care for healthy hair.

Women

Women typically suffer diffuse hair loss and thinning hair

(often hormonal).

It starts on the top and crown of the scalp. Female hair loss rarely leads to baldness – as it can do for men.

Women generally experience temporary hair loss or thinning which can be due to hormonal changes such as pregnancy and the menopause, stress factors, medication, chronic disease, overuse of chemicals on the hair and environmental factors.

In women age-related hair loss usually occurs only after menopause. The production of female sex hormones is reduced and the hair follicle-damaging effect of dihydrotestosterone may come to the fore. Therefore, women can be affected also by hormonal hair loss as men after menopause. The previously healthy hair looks thin and lifeless.

More severe hair loss can result in female pattern baldness where there is a family history of female pattern baldness as well as some of the above mentioned causes. The reason for female pattern baldness is not fully understand.  In women the hair thins usually along the crest.

Diffuse hair loss

The different causes of diffuse hair loss

A hair loss of up to 100 hairs a day is considered normal. If the hair loss exceed this figure, there may be different causes – for example, pregnancy, taking certain medications and a poor diet.

Hair loss during pregnancy and after birth

Women often lose hair in the two to three months after childbirth (postpartum effluvium): This is because, during pregnancy, estrogen levels in the blood are very high. With the birth of a child this will drop sharply and may result in hair loss as the hair grows from the growth stage to the resting stage. Once the hormone levels return to normal, the hair loss should stop. Normally the pregnancy-related diffuse hair loss ends six months after the birth of a child.

Circular hair loss (alopecia areata)

When circular hair loss (alopecia areata) occurs – usually temporary – the loss of hair in a limited, usually circular or oval area with a diameter of two to 2.5 centimetres. Alopecia areata can occur regardless of age or gender. The cause of alopecia areata is unknown. Doctors may recommend taking measures to help strengthen the immune system and reduce stress factors.  Once the body immunity has recovered, and the hair will grow back.

Hair loss caused by the misapplication of cosmetic products

Many cosmetic products contain synthetic substances which may cause irritation or allergic reactions of the scalp. The misapplication of such products may disturb the balance of the scalp and may result in hair loss.

Hair loss due to taking medication

Some medications – for example, blood coagulation preparations, antidepressants, antihypertensive, the birth control pill or high doses of vitamin A – can damage the hair roots and lead to diffuse hair loss, especially with long-term use.

Hair loss due to unbalanced and inadequate nutrition

Iron, zinc, sulphur and vitamins of the B group care for healthy hair. People who do not have a balanced diet may experience hair loss.