الفهرس 
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Abstract
Androgenetic alopecia, or pattern alopecia, is an extremely common disorder affecting both men and women. The incidence of androgenetic alopecia is generally considered to be greater in males than females.
Androgenetic alopecia is a genetically determined disorder and is progressive through the gradual conversion of terminal hairs into indeterminate hairs and finally to vellus hairs. Patients with androgenetic alopecia have a reduction in the terminal-to-vellus hair ratio. The onset of androgenetic alopecia is gradual. Men present with gradual thinning in the temporal areas, producing a reshaping of the anterior part of the hairline.
In both males and females with androgenetic alopecia, the transition from large, thick, pigmented terminal hairs to thinner, shorter, indeterminate hairs and finally to short, wispy, non-pigmented vellus hairs in the involved areas is gradual.
In men androgenetic alopecia usually follows a defined pattern, beginning with bi-temporal recession of the frontal hairline. This is followed by diffuse thinning over the vertex (top) of the scalp, eventually leading to complete hair loss in this region.
Women do not suffer classic male pattern baldness. Three different clinical patterns have been described: the Ludwig pattern, the Hamilton pattern and the christmas tree pattern. The first clinical presentation of AGA in women generally includes diffuse thinning over the fronto-parietal scalp with a preserved frontal hairline.
A variety of genetic and environmental factors likely play a role in causing androgenetic alopecia. Researchers have determined that this form of hair loss is related to hormones called androgens, particularly an androgen called dihydrotestosterone. Researchers continue to investigate the connection between androgenetic alopecia and other medical conditions, such as coronary heart disease and prostate cancer in men and polycystic ovary syndrome in women. They believe that some of these disorders may be associated with elevated androgen levels, which may help explain why they tend to occur with androgen-related hair loss.