Biology of Androgenetic Alopecia: Significance of Androgen Metabolism

Takayasu Susumu

doi:10.14924/dermatol.111.131

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Other Title

男性型脱毛の皮膚生物学―アンドロゲンの影響を中心に―
生涯教育講座男性型脱毛の皮膚生物学 : アンドロゲンの影響を中心に
ショウガイキョウイクコウザダンセイガタダツモウノヒフセイブツガク : アンドロゲンノエイキョウオチュウシンニ

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Description

In the fronto—parietal scalp in androgenetic alopecia, hair follicles gradually become minuaturized, and the anagen period becomes shorter. Recent clinical findings clearly show that the type 2 isozyme of 5 α-reductase（5 αR2）, which converts testosterone to dihydrotestosterone, plays a crucial role in beard growth and the development of androgenetic alopecia. Patients with 5 αR 2 deficiency possess less facial hair and do not become bald. In addition, finasteride, a 5 αR 2 inhibitor, partially reverses hair loss in androgenetic alopecia. There is considerable evidence to suggest that the dermal papilla plays a key role in hair growth and mediates the action of androgen. 5 αR of cultured beard dermal papilla cells shows the characteristics of the type 2 isozyme；the isozyme pattern of 5 αR in those from balding scalp remains unknown. Follicular epithelium such as the outer root sheath and hair matrix exhibits the activity of 5 αR 1. Freshly isolated hair follicles, containing both epithelial and mesenchymal portions, have been shown to have both 5 αR1 and5 αR 2 activities, and those from balding scalp have three times higher activity of 5 αR 2 than those from the occipital scalp.

Journal

The Japanese Journal of Dermatology

The Japanese Journal of Dermatology 111 (2), 131-137, 2001

Japanese Dermatological Association

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