Androgens and alopecia

• Published in: Molecular and cellular endocrinology Vol. 198; no. 1; pp. 89 - 95
• Main Author: Kaufman, Keith D
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 30.12.2002
• Subjects: 3-Oxo-5-alpha-Steroid 4-Dehydrogenase - metabolism; 5-alpha Reductase Inhibitors; Alopecia - drug therapy; Alopecia - physiopathology; Androgenetic alopecia; Androgens - metabolism; Clinical Trials, Phase III as Topic; Dihydrotestosterone; Dihydrotestosterone - metabolism; Enzyme Inhibitors - metabolism; Enzyme Inhibitors - therapeutic use; Female; Female pattern hair loss; Finasteride; Finasteride - metabolism; Finasteride - therapeutic use; Hair Follicle - growth & development; Hair Follicle - physiology; Humans; Male; Male pattern hair loss; Randomized Controlled Trials as Topic; Scalp - anatomy & histology; Scalp - metabolism; Twin Studies as Topic; Male pattern hair loss; Female pattern hair loss; Dihydrotestosterone; Finasteride; Androgenetic alopecia
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/S0303-7207(02)00372-6

Androgens have profound effects on scalp and body hair in humans. Scalp hair grows constitutively in the absence of androgens, while body hair growth is dependent on the action of androgens. Androgenetic alopecia, referred to as male pattern hair loss (MPHL) in men and female pattern hair loss (FPHL) in women, is due to the progressive miniaturization of scalp hair. Observations in both eunuchs, who have low levels of testicular androgens, and males with genetic 5α-reductase (5αR) deficiency, who have low levels of dihydrotestosterone (DHT), implicate DHT as a key androgen in the pathogenesis of MPHL in men. The development of finasteride, a type 2-selective 5αR inhibitor, further advanced our understanding of the role of DHT in the pathophysiology of scalp alopecia. Controlled clinical trials with finasteride demonstrated improvements in scalp hair growth in treated men associated with reductions in scalp DHT content, and a trend towards reversal of scalp hair miniaturization was evident by histopathologic evaluation of scalp biopsies. In contrast to its beneficial effects in men, finasteride did not improve hair growth in postmenopausal women with FPHL. Histopathological evaluation of scalp biopsies confirmed that finasteride treatment produced no benefit on scalp hair in these women. These findings suggest that MPHL and FPHL are distinct clinical entities, with disparate pathophysiologies. Studies that elucidate the molecular mechanisms by which androgens regulate hair growth would provide greater understanding of these differences.