Measuring reversal of hair miniaturization in androgenetic alopecia by follicular counts in horizontal sections of serial scalp biopsies: results of finasteride 1 mg treatment of men and postmenopausal women.

Hair regrowth was evaluated by histologic analysis in men and women treated for androgenetic alopecia, by counting follicles in horizontal sections of scalp biopsies. Serial 4mm punch biopsies were taken at baseline and after 12mo of treatment from the transitional area of hair thinning between normal hair and vertex balding in men, and in an area of frontal/parietal thinning in women. Horizontal sections of reticular and papillary dermis were read by one observer, blinded to patient, treatment, and time. All terminal hair bulbs, terminal anagen and telogen hairs, and vellus and vellus-like miniaturized hairs were counted. Twenty-six men aged 18-41y, comprising 14 on finasteride 1 mg daily and 12 on placebo, and 94 postmenopausal women, aged 41-60y, comprising 44 on finasteride 1 mg daily and 50 on placebo, were evaluated. In the male study, the terminal hairs increased from a mean baseline count of 15.5-20.9 after 12mo of finasteride, versus 17.3-18.3 in the placebo patients. The miniaturized hairs decreased from 26.7 to 23.6 with finasteride versus 21.3-20.3 with placebo. The terminal-to-vellus ratio increased more in the finasteride than in the placebo patients, suggesting some reversal of the miniaturization process with finasteride. In the female study, no significant differences in follicular counts were found between the finasteride and placebo groups after 12mo of treatment. Follicular counts in horizontal sections provide an informative adjunct to noninvasive measures used in hair growth studies. Finasteride appears to be capable of reversing hair miniaturization in androgenetic alopecia in young to middle-aged men, but not in postmenopausal women.