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Finasteride and the hair cycle

2000; Elsevier BV; Volume: 42; Issue: 5 Linguagem: Inglês

10.1067/mjd.2000.103272

1097-6787

Antonellá Tosti, Bianca Maria Piraccini,

Historical Gender and Feminism Studies

The article by Leyden and associates "Finasteride in the Treatment of Men with Frontal Male Pattern Hair Loss" (J Am Acad Dermatol 1999;40:930-7) shows that the hair count increases during the first months of treatment and remains stable after the first year; clinical improvement continues to increase over time. We give further evidence of a double effect of finasteride on hair growth. The increase in the hair count observed during the first year of treatment indicates that the drug actively promotes the re-entry of resting follicles into the anagen phase, including those follicles that have abnormally prolonged their telogen phase. These follicles are empty because they have shed the telogen shaft before starting the production of a new hair shaft, as occurs in normal follicles. The phenomenon of the "empty follicles" strongly contributes to the hair thinning that clinically characterizes androgenetic alopecia.1Courtois M Loussauarn G Hourseau C Grollier JF. Ageing and hair cycles.Br J Dermatol. 1995; 132: 86-93Crossref PubMed Scopus (176) Google Scholar, 2Guarrera M Rebora A. Anagen hairs may fail to replace telogen hairs in early androgenetic female alopecia.Dermatology. 1996; 192: 28-31Crossref PubMed Scopus (44) Google Scholar Differences in the increase of the hair count between different patients and different scalp areas3Kaufman KD Olsen EA Whiting D Savin R De Villez R Bergfeld W et al.Finasteride in the treatment of men with androgenetic alopecia.J Am Acad Dermatol. 1998; 39: 578-589Abstract Full Text Full Text PDF PubMed Scopus (541) Google Scholar may partially be related to the magnitude of the empty follicle phenomenon at baseline. The anagen-promoting effect of finasteride (increase in the hair count) is evident during the first year of treatment and is responsible for the "early improvement" noticed as early as the third month of treatment in some patients. The continuous improvement of the subjective assessments (patient self-assessment, investigator assessment, global photography assessment) after the first year of treatment is not related to the hair count that remains stable but to the action of finasteride on anagen growth. The prolongation of anagen induced by the drug results in progressive thickening and elongation of miniaturized and intermediate hair. This effect explains why patients continue to experience improvement of the appearance of the hair even if the hair count remains stable. Therefore hair count and subjective assessments document two different phenomena (Table I), which may be independent, and we should keep in mind that patients may clinically improve even if their hair count does not considerably increase.Table IEffects of finasterideEarly (3-6 mo)Induction of anagen→ Increased hair countDecreased anagen sheddingLate (after 1 y)Prolongation of anagen→Hair thickening and elongation→Improvement in the hair quality Open table in a new tab