Although there are various causes of hair loss such has hypothyroidism, immunological problems, drugs, and anemia, the most common cause is associated with the hormone dihyrotestosterone.
Hair grows from follicles which are very small pouches located in the skin.
Dihyrotes-tosterone causes these follicles to become even smaller and the hair becomes very short, fine, and lacks normal pigment. It also reduces the time for hair to properly grow. This type of hair loss has been termed androgenetic alopecia or aga. Some treatment is available for this type of hair loss. The medication propecia, which is taken orally, decreases the amount of dihydrotestostorone present thereby preventing the shrinkage of the hair follicles.