
Your hair goes through a cycle of growth and rest. The course of each cycle varies by individual. But in general, the growth phase of scalp hair, known as anagen, typically lasts two to three years. During this time, your hair grows about 1 centimeter (just less than 1/2 inch) a month. The resting phase is called telogen. This phase typically lasts three to four months. At the end of the resting phase, the hair strand falls out and a new one begins to grow in its place. Once a hair is shed, the growth stage begins again.
Most people normally shed 50 to 100 hairs a day. But with about 100,000 hairs in the scalp, this amount of hair loss shouldn't cause noticeable thinning of the scalp hair.
Gradual thinning is a normal part of aging. However, hair loss may lead to baldness when the rate of shedding exceeds the rate of regrowth, when new hair is thinner than the hair shed or when hair comes out in patches.
Other causes of hair loss
* Poor nutrition. Having inadequate protein or iron in your diet or poor nourishment in other ways can cause you to experience hair loss. Fad diets, crash diets and certain illnesses, such as eating disorders, can cause poor nutrition.
* Medications. Certain drugs used to treat gout, arthritis, depression, heart problems and high blood pressure may cause hair loss in some people. Taking birth control pills also may result in hair loss for some women.
* Disease. Diabetes and lupus can cause hair loss.
Hormonal changes.
Hormonal changes and imbalances can cause temporary hair loss. This could be due to pregnancy, having a baby, discontinuing birth control pills, beginning menopause, or an overactive or underactive thyroid gland. The hair loss may be delayed by three months following a hormonal change, and it'll take another three months for new hair to grow back. During pregnancy, it's normal to have thicker, more luxuriant hair. It's also common to lose more hair than normal about three months after delivery. If a hormonal imbalance is associated with an overproduction of testosterone, there may be a thinning of hair over the crown of the scalp. Correcting hormonal imbalances may stop hair loss.


