Andrew Messenger and Rodney Sinclair*

Departments of Dermatology, Royal Hallamshire Hospital, Sheffield, UK and St Vincent’s Hospital*, Melbourne, Australia

Previous studies on the pathology of female pattern hair loss (FPHL) have reported an increased proportion of follicles in telogen and an increased proportion of vellus follicles, manifest as a low terminal:vellus (T:V) ratio. The aim of this study was to establish whether the low T:V ratio in FPHL is due to a genuine increase in the number of vellus hairs, indicating a process of follicular miniaturisation, or to a preferential reduction in terminal follicles numbers that may occur if hair loss is due to prolongation of the latent period (kenogen) of the hair cycle alone.

We studied 43 women complaining of hair loss. The severity of the hair loss was graded clinically on a 5-point scale from 1 (no obvious hair loss) to 5 (severe hair loss). Three 4mm punch biopsies were taken from the frontal scalp of each patient, sectioned horizontally and stained with H&E. Two levels were studied on each biopsy – through the mid-infundibular region and through mid-isthmus. The following were counted – total follicles, terminal follicles, vellus follicles (according to the Whiting criteria), anagen and telogen/catagen follicles. The results from the three biopsies from each subject were averaged and statistical evaluations performed on the meaned values. There was a progressive decline in mean total follicle count with increasing grade of hair loss (Grade: 1 345/cm², Grade 5: 217/cm²) and a more rapid reduction in terminal follicle counts (Grade: 1 263/cm², Grade 5: 96/cm²). The absolute number of vellus follicles increased from 33/cm² (Grade 1) to 71/cm² (Grade 4) declining to 51/cm² at Grade 5. The T:V ratio fell from 12.8 (Grade 1) to 2.3 (Grade 4) and remained at this level thereafter. The proportion of follicles in telogen increased from 13.7% (Grade 1) to 31.4% (Grade 5).

Our results confirm that there is an increase in vellus follicle numbers with increasing severity of hair loss in women with FPHL, indicating that terminal follicles do indeed miniaturise. It is possible that there is also an increase in the number of follicles in a latent stage of telogen but this was difficult to assess from our data. The fall in total follicle counts with stabilising of the T:V ratio suggest that miniaturisation does not stop with a vellus follicle but may progress to follicular deletion.