No abstract

Hair's importance in human communication means that abnormalities like excess hair in hirsutism or hair loss in alopecia cause psychological distress. Androgens are the main regulator of human hair follicles, changing small vellus follicles producing tiny, virtually invisible hairs into larger intermediate and terminal follicles making bigger, pigmented hairs. The response to androgens varies with the body site as it is specific to the hair follicle itself. Normally around puberty, androgens stimulate axillary and pubic hair in both sexes, plus the beard, etc. in men, while later they may also inhibit scalp hair growth causing androgenetic alopecia. Androgens act within the follicle to alter the mesenchyme-epithelial cell interactions, changing the length of time the hair is growing, the dermal papilla size and dermal papilla cell, keratinocyte and melanocyte activity. Greater understanding of the mechanisms of androgen action in follicles should improve therapies for poorly controlled hair disorders like hirsutism and alopecia.

Androgens can gradually transform large scalp hair follicles to smaller vellus ones, causing balding. The mechanisms involved are unclear, although androgens are believed to act on the epithelial hair follicle via the mesenchymederived dermal papilla. This study investigates whether the levels and type of androgen receptors in primary lines of cultured dermal papilla cells derived from balding scalp hair follicles differ from those of follicles from non-balding scalp.Androgen receptor content was measured by saturation analysis using the non-metabolisable androgen, [3 H]mibolerone (0·05-10 nM) in a 9-10 point assay. Pubic dermal fibroblasts and Shionogi cells were examined as positive controls. Repetitive assays of Shionogi cells showed good precision in the levels of androgen receptor content (coefficient of variation=3·7%). Specific, high affinity, low capacity androgen receptors were detected in dermal papilla cells from both balding and non-balding follicles. Balding cells contained significantly (P<0·01) greater levels of androgen receptors (B max =0·06 0·01 fmol/10 4 cells (mean ...)) than those from non-balding scalp (0·04 0·001). Competition studies with a range of steroids showed no differences in receptor binding specificity in the two cell types.The higher levels of androgen receptors in cells from balding scalp hair follicles with similar properties to those from non-balding scalp concur with the expectations from their in vivo responses to androgens. This supports the hypothesis that androgens act via the dermal papilla and suggests that cultured dermal papilla cells may offer a model system for studying androgen action in androgenetic alopecia.

No abstract

Various parameters of hair growth were determined every 28 days for 18 months in 14 healthy Caucasian men aged 18-39 with indoor occupations in Sheffield, U.K. (latitude 53.4 degrees N). In the scalp the proportion of follicles in anagen reached a single peak of over 90% in March, and fell steadily to a trough in September. The number of shed hairs reached a peak around August/September, when least follicles were in anagen. At this time the average loss of hairs was about 60 per day, more than double that during the preceding winter. The rate of growth of the beard was lowest in January and February and increased steadily from March to July to reach a peak about 60% above the winter level. The rate of growth of thigh hair showed a similar pattern though with less pronounced differences. No seasonal fluctuations in finger- or toenail growth were detected.