A normal person loses around 100 hairs a day that get shed at the end of their growth cycle. But this hair loss usually goes unnoticed.
Each hair undergoes three stages of development. Around 85 to 90% of hair follicles on the head are usually in the anagen or growing stage. They remain in this stage for 2 to 6 years. This is followed by the catagen or involution phase that affects 2 to 3% of hair follicles.
The catagen phase is followed by the telogen or resting phase in which 10 to 15% of hair follicles undergo a period of rest for around 3 months. Following this stage, the hair is ejected from the skin leaving a solid, hard nodule.
Some degree of hair loss is thus normal. If there is excessive hair loss, it makes sense to first find out the possible cause so that the best treatment can be adopted.
The cause of hair loss may vary from a local condition affecting the scalp to an ailment affecting the whole body.
1. Androgenetic alopecia:
The most common type of hair loss is related to both the genetic and hormonal make up, and is called androgen-dependent hair loss or androgenetic alopecia. The commonly used name for this type of hair loss is male or female pattern baldness.
About 50% of children with a balding parent of either any mens will become bald over a period of time. In the United States, an estimated 50 million men and 30 million women are affected by male and female pattern baldness, respectively.
Male pattern baldness runs in families and is characterized by a receding hairline, and moderate to extensive loss of hair, especially on the crown area. The hair is lost in an M-shaped pattern, with loss at the crown and temples and sparing of the sides and the back of the head.
The main cause of this condition is the presence of high amounts of the male hormone, dihydrotestosterone (DHT) within the hair follicle. DHT is produced from testosterone in the prostate, the scalp and other organs. The abundance of DHT causes the hair follicle to degrade and shortens the active phase of the hair.
Male pattern baldness is also associated with coronary heart disease, enlargement of prostate and its cancer, disorders of insulin resistance and high blood pressure.
Female pattern baldness is characterized by overall thinning of hair on the head, and a moderate loss of hair on the crown or at the hairline. Women with this type of baldness may show excess androgen levels and should be evaluated for other conditions like polycystic ovarian syndrome (PCOS) characterized by irregular menstruation, excess body hair, acne and weight gain.
2. Alopecia areata:
Alopecia areata or “spot baldness” is a condition where the patient suffers from a localized hair loss.
When the hair loss extends to the whole scalp, the condition is called alopecia totalis. If it is accompanied by hair loss over the entire body, it is called alopecia universalis.
The hairs over the affected area resemble exclamation points, that is, the hair is thinned out but the caliber of the hair at the base remains the same. It may be associated with autoimmune conditions.
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