Hair Loss

Hair Structure
Hair consists of two parts- the hair follicle and the hair shaft. It is composed of a protein called keratin. Each hair strand has three layers. The innermost layer, or medulla is found in large, thick layer. The cortex – or the middle layer-gives the hair its strength, colour and texture. The outermost layer, cuticle, protects the cortex.

The hair root is enclosed within the hair follicle, and the dermal papilla lies at its base. The root is nourished by the bloodstream, which helps the new hair to sprout up. This hair follicle is influenced by the action of the male hormones or androgens which causes it to progressively shrink and thin down in genetically predisposed people.

Hair growth is a cyclical process. It has three alternating phases – Anagen, Catagen and Telogen. Anagen ( Growing phase) lasts for 3-5 years, catagen for 2 weeks and telogen ( resting phase) for 3 months. The usual ratio of anagen : telogen is 12:1. Normal hair shedding occurs in the telogen phase. The sensitivity of dermal papilla to androgenetic hormones is increased in alopecia patients. The increased level of androgens lead to shortening of the anagen phase of the hair cycle without affecting the telogen stage. As a result of this, the ratio of anagen: telogen decreases from the usual 12:1. Thus, the number of hair in anagen phase ( which cover the scalp) keeps on progressively decreasing with every cycle and telogen or the resting hair keeps on increasing resulting in bald spots on the scalp.