Androgenetic alopecia is the most common type of hair loss in humans. Its prevalence in any population has not been accurately studied, but it occurs much more often in Caucasians than in other races (6). Androgenetic alopecia affects approximately 50% of men over 40 years of age and may also affect just as many women (7). It occurs in both men and women as a result of genetic and hormonal factors.
Androgenetic alopecia appears to be autosomal dominant with gene expression apparently determined by hair follicle location (7). Expression of androgenetic alopecia can vary considerably from one person to another. In androgenetic alopecia, genetically predisposed hair follicles become progressively miniaturized over time. In men, the thick, pigmented terminal hairs in the affected area of the scalp eventually are replaced by the fine, unpigmented vellus hairs. Eventually, the affected scalp may become completely devoid of any hair. Women, however, rarely become completely bald but usually experience thinning characterized by an intermixing of the normal terminal hairs with finer vellus hairs (7). In both men and women, the hair growth cycle is altered, with fewer hairs in the anagen stage and more hairs in the telogen stage for longer periods of time (7).
Although scalp hair growth is not androgen-dependent, androgens are necessary for the full expression of androgenetic alopecia whereby they diminish |
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