Many theories suggest that male pattern baldness results from sexual selection. Many suggest that bald men are more virile or sexually active than men with full heads of hair. Although there is yet to be comprehensive evidence either way scientists have agreed that the levels of testosterone and DHT have a significant influence in hair loss.

Many primate species also experience baldness after puberty. In some species the male will encourage frontal hair loss and it appears that frontal balding conveys increased status and maturity to the social group. In humans the response to baldness is extremely variable. Although widely acceptable for men it can be a point of stigma for women.

Fortunately the advancement in hair replacement techniques has made it possible to manage the condition to a certain extent and recover a more socially acceptable head of hair. Here is a look at a number of causes of hair loss.

Trichotillomania

Trichotillomania occurs when the person suffering from the condition compulsively pulls out their own hair. It is classified as an impulse control disorder in which the person pulls out their own hair. This can be the hair on their head, eyebrows, eyelashes, facial hair, nose hair, pubic hair and other body hair. This typically results in noticeable bald patches.

Typically the condition begins in people as young as twelve and it has been recognised in people as old as seventy. In this type of baldness the hairs are not absent from the scalp but are instead broken and not visible. This suggests that they can grow back if they are given the opportunity.

Radiation

Radiation can cause hair loss. Typical examples of this are people that receive radiation therapy for the treatment of cancer. Typically the hair at the point where the treatment is administered can become bald. The area can also become irritated but it can be a type of hair loss that will eventually replenish itself. After treatment the affected area can recover and achieve normal levels of hair growth.

Fungal infection

Some fungal infections can result in massive cases of hair loss. Caused by contact with a yeast or fungus this type of baldness can result in itching that develops to patches of hair loss. The affected area can turn red and experience weeping before losing hair. In this case the hair loss is not permanent as the follicles still exist to produce the hair. As a result when the infection is treated the hair is likely to grow back. This type of hair loss is common in children.

Autoimmune disorder

Alopecia areata is a type of hair loss that causes baldness in patches of hair. Also known as 'spot baldness' it can affect just one area of the body or in some cases every hair on the entire body. It usually affects the scalp and causes patches of baldness.

The spots of baldness may be slightly tender and it may tingle. In a very small number of cases it spreads to affect the whole of the scalp. It occurs in both men and women. It is not contagious but there are suggestions that it is hereditary. Many people that have alopecia areata have relatives that suffer from autoimmune disorders.

Hypothyroidism

Hypothyroidism is a disease in which the sufferer experiences an insufficient production of the thyroid hormone by the thyroid gland. This can result in hair loss. The thyroid hormone is involved in an enormous range of the body's functions therefore if it falls out of balance it can result in a wide variety of symptoms. The hair loss that it causes often occurs at the front part of the scalp and the outer edge of the eyebrows.