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HAIR LOSS » Hair Loss Causes
Genetic (Androgenetic Alopecia)

It is not uncommon in today's society to think of having hair as normal and losing hair as abnormal. However, the principal cause of hair loss in men is not abnormal in the sense of being a bizarre phenomenon. It is better described as a normal phenomenon that causes hair loss ranging from almost undetectable loss to balding over most of the scalp. This cause of hair loss is androgenetic alopecia, also called male-pattern hair loss. A variant form is called female-pattern hair loss. It involves some causative factors that are the same and some that may be different from those associated with male-pattern hair loss.

The incidence of androgenetic alopecia has not been extensively studied in all populations. Its incidence in the most-studied population of Caucasians may be near 100% when the study includes minor shifts of hair growth from mature hair to vellus ("peach fuzz") hair with advancing age. Androgenetic alopecia that is apparent enough to be characterized as a "type" occurs in 50% or more of both men and women.

Types of Hair Loss Due to Androgenetic Alopecia

Types of male- and female-pattern hair loss graded by severity are illustrated in charts. These charts are standardized guides for assessing the progression of androgenetic alopecia. While the charts are used as standard guides, they are not universally applicable; some variant patterns of hair loss do not fall clearly into any "type", but may show characteristics of two or more of the charted types.

From article:
Hair Loss and Its Causes