Reason for Hair Loss

Each strand of hair on your head goes through a growth period of two to 10 years, and then a resting stage of two to three months before it is shed. People normally shed 50 to 100 hairs every day, a tiny fraction of the roughly 100,000 hairs in their scalp. But, undeniably, for many people, hair loss can accelerate and result in partial or total baldness. There are several common reasons for hair loss, most of which are temporary with appropriate treatment.

Heredity

• Most hair loss is a result of genetics. At a period in life ranging from the late teens to late middle age, the growth period of hair shortens, and each strand becomes thinner and falls out more easily. This process, called androgenetic alopecia, is more commonly known as male-pattern baldness though it occurs in females as well. Several topical applications are available that can slow the process. As the name suggests, however, androgenic alopecia is only partly caused by heredity; there's also a strong correlation to changing hormone levels.

Testosterone

• Androgenic alopecia is associated with lower total testosterone levels and higher levels of androgens, such as dihydrotestosterone (DHT). It's believed that excess DHT can interfere with hair follicles, preventing hair growth. The enzyme 5-alpha-reductase converts testosterone into DHT, and drugs that interfere with this enzyme are used to treat male-pattern baldness. Another natural molecule, called SHBG, is essential to preventing the process of converting testosterone into DHT. SHBG is broken down in the presence of insulin, however, and high insulin levels are also correlated with certain expressions of male-pattern baldness.

Thyroid

• The thyroid gland, located in the neck near the throat, secretes a hormone called thyroxin, which regulates the body's metabolism. Both hypo- and hyperthyroidism cause metabolic disturbances that can lead to hair loss. Hypothyroidism, which is not an uncommon cause of low metabolism in women, can lead to androgenic alopecia because it encourages the conversion of testosterone into DHT. If prolonged, the resulting effect is pattern baldness in both men and women.

Immune Disorder

• Another form of hair loss is alopecia areata. Its causes are unknown, but it is classified as an autoimmune disorder. It's believed the body creates antibodies to the hair, which attack the follicles and prevent hair growth. This type of hair loss is usually temporary, but can recur several times during a person's life. It is characterized by loss of small coin-sized patches at a time, sometimes revealing red or oily patches on the scalp. There is thought to be a genetic predisposition to alopecia areata, and that this type of hair loss can be triggered by factors in the environment.

Stress

• Telogen effluvium is the name for hair loss that occurs because of stress. A severe physical or emotional shock can prematurely end the growth phase of large numbers of hair. After the two to three month resting period, these hairs fall out, resulting in a significant and sudden hair loss. Assuming the condition that initially caused the stress is resolved, hair loss caused by stress is usually temporary.

Other Reasons

• There are several other common reasons for hair loss. Inadequate levels of essential protein and iron in the diet can cause hair loss. Certain medications and medical treatments, most notably radiation therapy, can result in loss of hair. Skin infections like ringworm, a fungal infection, can cause localized hair loss. Severe or over treatment of hair with chemical dyes, bleaches, and straighteners can result in hair loss as well. All of these causes are usually temporary, with hair regrowing when the causing factor is removed.