Hair loss is a universal and inevitable phenomenon for many people. Despite its physiological basis, hair presents such a powerful role for psychosexual image of human being that its loss has forced people to search for a remedy for centuries.
In order to find a cure for hair loss, the underlying reasons of hair loss should be well identified. The mechanism of hair loss has been recently described.
Hamilton defined Androgenetic Alopecia (AGA) (male type hair loss) in 1942.
Androgenetic hair loss comprises 95% of all hair losses in humans. Although it is common among men, it has also been reported in women. Until 30 years of age, 50% of men and 20% of women experience some hair loss. The mechanism of Androgenetic hair loss rests on the negative effect of testosterone known as male hormone on hair roots. This kind of hair fall- out, also called 'male type hair loss', develops characteristically by receding from the temples, followed by thinning of hair on the crown and then becoming scarce. In women, androgenetic hair loss is widespread on the crown. Contrary to men, the hairline of the temples does not recede.
Androgenetic hair loss has been described according to Norwood Classification. The classification is used in determining the suitable candidates for hair transplantation, recording the examination results of patients, treatment follow-up, and standardizing the relevant data. Thus, a through knowledge of the classification is essential.
Other reasons of hair fall-out are as follows:
1. Normal hair loss: in line with the life cycle of the hair, a hair-loss of 100-150 hairs a day is considered normal.
2. Physiological hair loss: Loss of hair during pregnancy is an example. It is reversible.
3. Individually-based hair loss: It is inflicted by the person himself/herself. Tight hair pins may cause hair loss.
4. Infection related hair loss: occurs in some fungal infections.
5. Alopecia Areata: It is a localized or patchy form of hair loss. Proper treatment can reverse the condition.
6. Anagen Effluvium: hair loss due to exposure to radiation or certain chemicals.
7. Telogen Effluvium: Stress and chronic disease associated hair loss.
8. Damage of hair roots: inflicted by trauma and/or pressure.
